Index: docs/ref/models/fields.txt
===================================================================
--- docs/ref/models/fields.txt	(revision 16341)
+++ docs/ref/models/fields.txt	(working copy)
@@ -210,6 +210,10 @@
 field will raise. Pass in a dictionary with keys matching the error messages you
 want to override.
 
+Error message keys include ``null``, ``blank``, ``invalid``, ``invalid_choice``,
+and ``unique``. Additional error message keys are specified for each field in
+the `Field types`_ section below.
+
 ``help_text``
 -------------
 
@@ -416,7 +420,8 @@
     it's not just a default value that you can override.
 
 The admin represents this as an ``<input type="text">`` with a JavaScript
-calendar, and a shortcut for "Today".
+calendar, and a shortcut for "Today". Includes an additional ``invalid_date``
+error message key.
 
 .. note::
     As currently implemented, setting ``auto_now`` or ``auto_now_add`` to
Index: tests/modeltests/validation/models.py
===================================================================
--- tests/modeltests/validation/models.py	(revision 16341)
+++ tests/modeltests/validation/models.py	(working copy)
@@ -78,3 +78,7 @@
     slug = models.CharField(max_length=50, unique_for_year='posted', blank=True)
     subtitle = models.CharField(max_length=50, unique_for_month='posted', blank=True)
     posted = models.DateField(blank=True, null=True)
+
+class UniqueErrorsModel(models.Model):
+    name = models.CharField(max_length=100, unique=True, error_messages={'unique': u'Custom unique name message.'})
+    number = models.IntegerField(unique=True, error_messages={'unique': u'Custom unique number message.'})
\ No newline at end of file
Index: tests/modeltests/validation/test_unique.py
===================================================================
--- tests/modeltests/validation/test_unique.py	(revision 16341)
+++ tests/modeltests/validation/test_unique.py	(working copy)
@@ -7,7 +7,7 @@
 from django.utils import unittest
 
 from models import (CustomPKModel, UniqueTogetherModel, UniqueFieldsModel,
-    UniqueForDateModel, ModelToValidate, Post, FlexibleDatePost)
+    UniqueForDateModel, ModelToValidate, Post, FlexibleDatePost, UniqueErrorsModel)
 
 
 class GetUniqueCheckTests(unittest.TestCase):
@@ -149,3 +149,22 @@
             self.fail("unique_for_month checks shouldn't trigger when the associated DateField is None.")
         except:
             self.fail("unique_for_month checks shouldn't explode when the associated DateField is None.")
+
+    def test_unique_errors(self):
+        m1 = UniqueErrorsModel.objects.create(name='Some Name', number=10)
+        m = UniqueErrorsModel(name='Some Name', number=11)
+        try:
+            m.full_clean()
+        except ValidationError, e:
+            self.assertEqual(e.message_dict, {'name': [u'Custom unique name message.']})
+        except:
+            self.fail('unique checks should catch this.')
+
+        m = UniqueErrorsModel(name='Some Other Name', number=10)
+        try:
+            m.full_clean()
+        except ValidationError, e:
+            self.assertEqual(e.message_dict, {'number': [u'Custom unique number message.']})
+        except:
+            self.fail('unique checks should catch this.')
+            
\ No newline at end of file
Index: django/db/models/base.py
===================================================================
--- django/db/models/base.py	(revision 16341)
+++ django/db/models/base.py	(working copy)
@@ -782,9 +782,10 @@
         # A unique field
         if len(unique_check) == 1:
             field_name = unique_check[0]
-            field_label = capfirst(opts.get_field(field_name).verbose_name)
+            field = opts.get_field(field_name)
+            field_label = capfirst(field.verbose_name)
             # Insert the error into the error dict, very sneaky
-            return _(u"%(model_name)s with this %(field_label)s already exists.") %  {
+            return field.error_messages['unique'] %  {
                 'model_name': unicode(model_name),
                 'field_label': unicode(field_label)
             }
Index: django/db/models/fields/__init__.py
===================================================================
--- django/db/models/fields/__init__.py	(revision 16341)
+++ django/db/models/fields/__init__.py	(working copy)
@@ -60,6 +60,7 @@
         'invalid_choice': _(u'Value %r is not a valid choice.'),
         'null': _(u'This field cannot be null.'),
         'blank': _(u'This field cannot be blank.'),
+        'unique': _(u'%(model_name)s with this %(field_label)s already exists.'),
     }
 
     # Generic field type description, usually overriden by subclasses