diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -1249,7 +1249,7 @@
         pass
     return baseset(datarepr=('<max %r, %r>', subset, os))
 
-@predicate('merge([withbranch])', safe=True)
+@predicate('merge([withbranch], samebranch=True)', safe=True)
 def merge(repo, subset, x):
     """Changeset is a merge changeset
 
@@ -1260,13 +1260,18 @@
     possible to specify a regular expression by starting the pattern
     with "re:". This can be used to match more than one branch
     (e.g. "re:branch1|branch2").
+
+    It is also possible to only return merges where both parents belong to
+    the same branch by specifying samebranch=True. If samebranch=False is
+    set then only merges where both parents do not belong to the same branch
+    will be returned.
     """
     cl = repo.changelog
     # matchfn is a function that returns true when a revision is a merge
     matchfn = lambda r: cl.parentrevs(r)[1] != -1
 
     # i18n: "merge" is a keyword
-    args = getargsdict(x, 'merge', 'withbranch')
+    args = getargsdict(x, 'merge', 'withbranch samebranch')
     if 'withbranch' in args:
         withbranch = getstring(args['withbranch'],
                                _('withbranch argument must be a string'))
@@ -1277,6 +1282,24 @@
             # matches the withbranch pattern (which can be a literal or a regex)
             matchfn = lambda r: (cl.parentrevs(r)[1] != -1
                                  and branchmatcher(repo[r].p2().branch()))
+    samebranch = None
+    if 'samebranch' in args:
+        # i18n: "samebranch" is a keyword
+        samebranch = getboolean(
+            args['samebranch'],
+            _('samebranch argument must be a True or False'))
+    if samebranch is not None:
+        basematchfn = matchfn
+        # if samebranch was specified, build a new match function
+        # that on top of basematch checks if the parents belong (or not)
+        # to the same branch (depending on the value of samebranch)
+        def matchfn(r):
+            c = repo[r]
+            if not basematchfn(r):
+                return False
+            issamebranchmerge = c.p1().branch() == c.p2().branch()
+            return issamebranchmerge if samebranch else not issamebranchmerge
+
     return subset.filter(matchfn, condrepr='<merge>')
 
 @predicate('branchpoint()', safe=True)
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -1743,7 +1743,7 @@
 Test section lookup
 
   $ hg help revset.merge
-      "merge([withbranch])"
+      "merge([withbranch], samebranch=True)"
         Changeset is a merge changeset
   
         All merge revisions are returned by default. If a "withbranch" pattern
@@ -1753,6 +1753,11 @@
         expression by starting the pattern with "re:". This can be used to match
         more than one branch (e.g. "re:branch1|branch2").
   
+        It is also possible to only return merges where both parents belong to
+        the same branch by specifying samebranch=True. If samebranch=False is
+        set then only merges where both parents do not belong to the same branch
+        will be returned.
+  
   $ hg help glossary.dag
       DAG
           The repository of changesets of a distributed version control system
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -3016,6 +3016,28 @@
   (branch merge, don't forget to commit)
   $ hg commit -m "different branch merge 2"
 
+test that the merge revisions can be split between those where
+samebranch is True and those where it is False
+  $ log 'merge()'
+  6
+  11
+  13
+  15
+  17
+  19
+
+show merges with the same branch
+  $ log 'merge(samebranch=True)'
+  11
+  13
+  15
+  19
+
+show merges with other branches (but not the same branch)
+  $ log 'merge(samebranch=False)'
+  6
+  17
+
 show merges with a particular branch
   $ log 'merge(.a.b.c.)'
   11
@@ -3025,6 +3047,9 @@
   $ log 'merge(-a-b-c-)'
   6
 
+  $ log 'merge(".a.b.c.", samebranch=False)'
+  17
+
 show merges with multiple branches using a regex
   $ log 'merge("re:.a.b.c.")'
   6