diff --git a/docs/en/topics/datamodel.md b/docs/en/topics/datamodel.md
index bb437734a..be0f2a1c7 100755
--- a/docs/en/topics/datamodel.md
+++ b/docs/en/topics/datamodel.md
@@ -553,13 +553,25 @@ See `[api:DataObject::$has_many]` for more info on the described relations.
 	
 	  // can be accessed by $myTeam->ActivePlayers()
 	  public function ActivePlayers() {
-	    return $this->Players("Status='Active'");
+	    return $this->Players()->filter('Status', 'Active');
 	  }
 	}
 
 Note: Adding new records to a filtered `RelationList` like in the example above doesn't automatically set the 
 filtered criteria on the added record.
 
+### Relations on Unsaved Objects
+
+You can also set *has_many* and *many_many* relations before the `DataObject` is saved. This behaviour uses the
+`[api:UnsavedRelationList]` and converts it into the correct `RelationList` when saving the `DataObject` for the
+first time.
+
+This unsaved lists will also recursively save any unsaved objects that they contain.
+
+As these lists are not backed by the database, most of the filtering methods on `DataList` cannot be used on a
+list of this type. As such, an `UnsavedRelationList` should only be used for setting a relation before saving an
+object, not for displaying the objects contained in the relation.
+
 ## Validation and Constraints
 
 Traditionally, validation in SilverStripe has been mostly handled on the controller
diff --git a/model/ArrayList.php b/model/ArrayList.php
index 3496fe84c..dccd6b3e2 100644
--- a/model/ArrayList.php
+++ b/model/ArrayList.php
@@ -12,7 +12,7 @@ class ArrayList extends ViewableData implements SS_List, SS_Filterable, SS_Sorta
 	 * 
 	 * @var array
 	 */
-	protected $items;
+	protected $items = array();
 	
 	/**
 	 *
diff --git a/model/DataObject.php b/model/DataObject.php
index 112e8b019..a5f37b79c 100644
--- a/model/DataObject.php
+++ b/model/DataObject.php
@@ -157,6 +157,11 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 	 */
 	protected $components;
 
+	/**
+	 * Non-static cache of has_many and many_many relations that can't be written until this object is saved.
+	 */
+	protected $unsavedRelations;
+
 	/**
 	 * Returns when validation on DataObjects is enabled.
 	 * @return bool
@@ -1188,6 +1193,15 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 				}
 				
 				DB::manipulate($manipulation);
+
+				// If there's any relations that couldn't be saved before, save them now (we have an ID here)
+				if($this->unsavedRelations) {
+					foreach($this->unsavedRelations as $name => $list) {
+						$list->changeToList($this->$name());
+					}
+					$this->unsavedRelations = array();
+				}
+
 				$this->onAfterWrite();
 
 				$this->changed = null;
@@ -1365,6 +1379,15 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 				. " on class '$this->class'", E_USER_ERROR);
 		}
 
+		// If we haven't been written yet, we can't save these relations, so use a list that handles this case
+		if(!$this->ID) {
+			if(!isset($this->unsavedRelations[$componentName])) {
+				$this->unsavedRelations[$componentName] =
+					new UnsavedRelationList($this->class, $componentName, $componentClass); 
+			}
+			return $this->unsavedRelations[$componentName];
+		}
+
 		$joinField = $this->getRemoteJoinField($componentName, 'has_many');
 		
 		$result = new HasManyList($componentClass, $joinField);
@@ -1473,6 +1496,15 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 	 */
 	public function getManyManyComponents($componentName, $filter = "", $sort = "", $join = "", $limit = "") {
 		list($parentClass, $componentClass, $parentField, $componentField, $table) = $this->many_many($componentName);
+
+		// If we haven't been written yet, we can't save these relations, so use a list that handles this case
+		if(!$this->ID) {
+			if(!isset($this->unsavedRelations[$componentName])) {
+				$this->unsavedRelations[$componentName] =
+					new UnsavedRelationList($parentClass, $componentName, $componentClass); 
+			}
+			return $this->unsavedRelations[$componentName];
+		}
 		
 		$result = Injector::inst()->create('ManyManyList', $componentClass, $table, $componentField, $parentField,
 			$this->many_many_extraFields($componentName));
diff --git a/model/UnsavedRelationList.php b/model/UnsavedRelationList.php
new file mode 100644
index 000000000..39b52e973
--- /dev/null
+++ b/model/UnsavedRelationList.php
@@ -0,0 +1,432 @@
+<?php
+
+/**
+ * An ArrayList that represents an unsaved relation.
+ *
+ * has_many and many_many relations cannot be saved until after the DataObject they're
+ * on has been written. This List pretends to be a RelationList and stores the related
+ * objects in memory.
+ *
+ * It can store both saved objects (as IDs) or unsaved objects (as instances of
+ * $dataClass). Unsaved objects are then written when the list is saved into an instance
+ * of RelationList.
+ *
+ * Most methods that alter the list of objects throw LogicExceptions.
+ */
+class UnsavedRelationList extends ArrayList {
+	/**
+	 * The DataObject class name that this relation is on
+	 * 
+	 * @var string
+	 */
+	protected $baseClass;
+
+	/**
+	 * The name of the relation
+	 * 
+	 * @var string
+	 */
+	protected $relationName;
+
+	/**
+	 * The DataObject class name that this relation is querying
+	 * 
+	 * @var string
+	 */
+	protected $dataClass;
+
+	/**
+	 * The extra fields associated with the relation
+	 *
+	 * @var array
+	 */
+	protected $extraFields = array();
+
+	/**
+	 * Create a new UnsavedRelationList
+	 *
+	 * @param string $dataClass The DataObject class used in the relation
+	 */
+	public function __construct($baseClass, $relationName, $dataClass) {
+		$this->baseClass = $baseClass;
+		$this->relationName = $relationName;
+		$this->dataClass = $dataClass;
+	}
+
+	/**
+	 * Add an item to this relationship
+	 *
+	 * @param $extraFields A map of additional columns to insert into the joinTable in the case of a many_many relation
+	 */
+	public function add($item, $extraFields = null) {
+		$this->push($item, $extraFields);
+	}
+
+	/**
+	 * Save all the items in this list into the RelationList
+	 *
+	 * @param RelationList $list
+	 */
+	public function changeToList(RelationList $list) {
+		foreach($this->items as $key => $item) {
+			if(is_object($item)) {
+				$item->write();
+			}
+			$list->add($item, $this->extraFields[$key]);
+		}
+	}
+
+	/**
+	 * Pushes an item onto the end of this list.
+	 *
+	 * @param array|object $item
+	 */
+	public function push($item, $extraFields = null) {
+		if((is_object($item) && !$item instanceof $this->dataClass)
+			|| (!is_object($item) && !is_numeric($item))) {
+			throw new InvalidArgumentException(
+				"UnsavedRelationList::add() expecting a $this->dataClass object, or ID value",
+				E_USER_ERROR);
+		}
+		if(is_object($item) && $item->ID) {
+			$item = $item->ID;
+		}
+		$this->extraFields[] = $extraFields;
+		parent::push($item);
+	}
+
+	/**
+	 * Get the dataClass name for this relation, ie the DataObject ClassName
+	 *
+	 * @return string
+	 */
+	public function dataClass() {
+		return $this->dataClass;
+	}
+
+	/**
+	 * Returns an Iterator for this relation.
+	 * 
+	 * @return ArrayIterator
+	 */
+	public function getIterator() {
+		return new ArrayIterator($this->toArray());
+	}
+
+	/**
+	 * Return an array of the actual items that this relation contains at this stage.
+	 * This is when the query is actually executed.
+	 *
+	 * @return array
+	 */
+	public function toArray() {
+		$items = array();
+		foreach($this->items as $key => $item) {
+			if(is_numeric($item)) {
+				$item = DataObject::get_by_id($this->dataClass, $item);
+			}
+			if(!empty($this->extraFields[$key])) {
+				$item->update($this->extraFields[$key]);
+			}
+			$items[] = $item;
+		}
+		return $items;
+	}
+
+	/**
+	 * Add a number of items to the relation.
+	 * 
+	 * @param array $items Items to add, as either DataObjects or IDs.
+	 * @return DataList
+	 */
+	public function addMany($items) {
+		foreach($items as $item) {
+			$this->add($item);
+		}
+		return $this;
+	}
+
+	/**
+	 * Returns true if the given column can be used to filter the records.
+	 */
+	public function canFilterBy($by) {
+		return false;
+	}
+
+
+	/**
+	 * Returns true if the given column can be used to sort the records.
+	 */
+	public function canSortBy($by) {
+		return false;
+	}
+
+	/**
+     * Remove all items from this relation.
+     */
+	public function removeAll() {
+		$this->items = array();
+		$this->extraFields = array();
+	}
+
+	/**
+	 * Remove the items from this list with the given IDs
+	 * 
+	 * @param array $idList
+	 */
+	public function removeMany($items) {
+		$this->items = array_diff($this->items, $items);
+		return $this;
+	}
+
+	/**
+	 * Removes items from this list which are equal.
+	 *
+	 * @param string $field unused
+	 */
+	public function removeDuplicates($field = 'ID') {
+		$this->items = array_unique($this->items);
+	}
+
+	/**
+	 * Sets the Relation to be the given ID list.
+	 * Records will be added and deleted as appropriate.
+	 * 
+	 * @param array $idList List of IDs.
+	 */
+	public function setByIDList($idList) {
+		$this->removeAll();
+		$this->addMany($idList);
+	}
+
+	/**
+	 * Returns the first item in the list
+	 *
+	 * @return mixed
+	 */
+	public function first() {
+		$item = reset($this->items);
+		if(is_numeric($item)) {
+			$item = DataObject::get_by_id($this->dataClass, $item);
+		}
+		if(!empty($this->extraFields[key($this->items)])) {
+			$item->update($this->extraFields[key($this->items)]);
+		}
+		return $item;
+	}
+
+	/**
+	 * Returns the last item in the list
+	 *
+	 * @return mixed
+	 */
+	public function last() {
+		$item = end($this->items);
+		if(!empty($this->extraFields[key($this->items)])) {
+			$item->update($this->extraFields[key($this->items)]);
+		}
+		return $item;
+	}
+
+	/**
+	 * Returns an array of a single field value for all items in the list.
+	 *
+	 * @param string $colName
+	 * @return array
+	 */
+	public function column($colName = 'ID') {
+		$list = new ArrayList($this->toArray());
+		return $list->column('ID');
+	}
+
+	/**
+	 * Set the ID of the record that this RelationList is linking.
+	 *
+	 * Adds the 
+	 *
+	 * @param $id A single ID, or an array of IDs
+	 */
+	public function setForeignID($id) {
+		$class = singleton($this->baseClass);
+		$class->ID = 1;
+		return $class->{$this->relationName}()->setForeignID($id);
+	}
+	
+	/**
+	 * Returns a copy of this list with the relationship linked to the given foreign ID.
+	 * @param $id An ID or an array of IDs.
+	 */
+	public function forForeignID($id) {
+		return $this->setForeignID($id);
+	}
+
+	/**
+	 * Return the DBField object that represents the given field on the related class.
+	 *
+	 * @param string $fieldName Name of the field
+	 * @return DBField The field as a DBField object
+	 */
+	public function dbObject($fieldName) {
+		return singleton($this->dataClass)->dbObject($fieldName);
+	}
+
+	/**#@+
+	 * Prevents calling DataList methods that rely on the objects being saved
+	 */
+	public function addFilter() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function alterDataQuery() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function avg() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function byIDs() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function byID($id) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function dataQuery() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function exclude() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function filter() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function getIDList() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function getRange($offset, $length) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function getRelationName() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function innerJoin() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function insertFirst() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function join() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function leftJoin() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function limit($length, $offset = 0) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function map($keyField = 'ID', $titleField = 'Title') {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function max() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function merge($with) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function min() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function newObject() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function offsetExists($offset) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function offsetGet($offset) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function offsetSet($offset, $value) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function offsetUnset($offset) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function pop() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function relation() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function removeByFilter() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function removeByID() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function reverse() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function setDataModel() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function setDataQuery() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function setQueriedColumns() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function shift() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function sql() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function subtract() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function sum() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function unshift($item) {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+
+	public function where() {
+		throw new LogicException(__FUNCTION__ . " can't be called on an UnsavedRelationList.");
+	}
+	/**#@-*/
+}
diff --git a/tests/model/UnsavedRelationListTest.php b/tests/model/UnsavedRelationListTest.php
new file mode 100644
index 000000000..57f011eb6
--- /dev/null
+++ b/tests/model/UnsavedRelationListTest.php
@@ -0,0 +1,184 @@
+<?php
+
+class UnsavedRelationListTest extends SapphireTest {
+	public static $fixture_file = 'UnsavedRelationListTest.yml';
+
+	protected $extraDataObjects = array('UnsavedRelationListTest_DataObject');
+
+	public function testReturnedList() {
+		$object = new UnsavedRelationListTest_DataObject;
+		$children = $object->Children();
+		$siblings = $object->Siblings();
+		$this->assertEquals($children, $object->Children(),
+			'Returned UnsavedRelationList should be the same.');
+		$this->assertEquals($siblings, $object->Siblings(),
+			'Returned UnsavedRelationList should be the same.');
+
+		$object->write();
+		$this->assertInstanceOf('RelationList', $object->Children());
+		$this->assertNotEquals($children, $object->Children(),
+			'Return should be a RelationList after first write');
+		$this->assertInstanceOf('RelationList', $object->Siblings());
+		$this->assertNotEquals($siblings, $object->Siblings(),
+			'Return should be a RelationList after first write');
+	}
+
+	public function testHasManyExisting() {
+		$object = new UnsavedRelationListTest_DataObject;
+
+		$children = $object->Children();
+		$children->add($this->objFromFixture('UnsavedRelationListTest_DataObject', 'ObjectA'));
+		$children->add($this->objFromFixture('UnsavedRelationListTest_DataObject', 'ObjectB'));
+		$children->add($this->objFromFixture('UnsavedRelationListTest_DataObject', 'ObjectC'));
+
+		$children = $object->Children();
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $children);
+
+		$object->write();
+
+		$this->assertNotEquals($children, $object->Children());
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $object->Children());
+	}
+
+	public function testManyManyExisting() {
+		$object = new UnsavedRelationListTest_DataObject;
+
+		$Siblings = $object->Siblings();
+		$Siblings->add($this->objFromFixture('UnsavedRelationListTest_DataObject', 'ObjectA'));
+		$Siblings->add($this->objFromFixture('UnsavedRelationListTest_DataObject', 'ObjectB'));
+		$Siblings->add($this->objFromFixture('UnsavedRelationListTest_DataObject', 'ObjectC'));
+
+		$siblings = $object->Siblings();
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $siblings);
+
+		$object->write();
+
+		$this->assertNotEquals($siblings, $object->Siblings());
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $object->Siblings());
+	}
+
+	public function testHasManyNew() {
+		$object = new UnsavedRelationListTest_DataObject;
+
+		$children = $object->Children();
+		$children->add(new UnsavedRelationListTest_DataObject(array('Name' => 'A')));
+		$children->add(new UnsavedRelationListTest_DataObject(array('Name' => 'B')));
+		$children->add(new UnsavedRelationListTest_DataObject(array('Name' => 'C')));
+
+		$children = $object->Children();
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $children);
+
+		$object->write();
+
+		$this->assertNotEquals($children, $object->Children());
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $object->Children());
+	}
+
+	public function testManyManyNew() {
+		$object = new UnsavedRelationListTest_DataObject;
+
+		$Siblings = $object->Siblings();
+		$Siblings->add(new UnsavedRelationListTest_DataObject(array('Name' => 'A')));
+		$Siblings->add(new UnsavedRelationListTest_DataObject(array('Name' => 'B')));
+		$Siblings->add(new UnsavedRelationListTest_DataObject(array('Name' => 'C')));
+
+		$siblings = $object->Siblings();
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $siblings);
+
+		$object->write();
+
+		$this->assertNotEquals($siblings, $object->Siblings());
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A'),
+			array('Name' => 'B'),
+			array('Name' => 'C')
+		), $object->Siblings());
+	}
+
+	public function testManyManyExtraFields() {
+		$object = new UnsavedRelationListTest_DataObject;
+
+		$Siblings = $object->Siblings();
+		$Siblings->add(new UnsavedRelationListTest_DataObject(array('Name' => 'A')), array('Number' => 1));
+		$Siblings->add(new UnsavedRelationListTest_DataObject(array('Name' => 'B')), array('Number' => 2));
+		$Siblings->add(new UnsavedRelationListTest_DataObject(array('Name' => 'C')), array('Number' => 3));
+
+		$siblings = $object->Siblings();
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A', 'Number' => 1),
+			array('Name' => 'B', 'Number' => 2),
+			array('Name' => 'C', 'Number' => 3)
+		), $siblings);
+
+		$object->write();
+
+		$this->assertNotEquals($siblings, $object->Siblings());
+
+		$this->assertDOSEquals(array(
+			array('Name' => 'A', 'Number' => 1),
+			array('Name' => 'B', 'Number' => 2),
+			array('Name' => 'C', 'Number' => 3)
+		), $object->Siblings());
+	}
+}
+
+class UnsavedRelationListTest_DataObject extends DataObject implements TestOnly {
+	public static $db = array(
+		'Name' => 'Varchar',
+	);
+
+	public static $has_one = array(
+		'Parent' => 'UnsavedRelationListTest_DataObject',
+	);
+
+	public static $has_many = array(
+		'Children' => 'UnsavedRelationListTest_DataObject',
+	);
+
+	public static $many_many = array(
+		'Siblings' => 'UnsavedRelationListTest_DataObject',
+	);
+
+	public static $many_many_extraFields = array(
+		'Siblings' => array(
+			'Number' => 'Int',
+		),
+	);
+}
diff --git a/tests/model/UnsavedRelationListTest.yml b/tests/model/UnsavedRelationListTest.yml
new file mode 100644
index 000000000..e0ffd14be
--- /dev/null
+++ b/tests/model/UnsavedRelationListTest.yml
@@ -0,0 +1,7 @@
+UnsavedRelationListTest_DataObject:
+    ObjectA:
+        Name: A
+    ObjectB:
+        Name: B
+    ObjectC:
+        Name: C