diff --git a/.travis.yml b/.travis.yml
index f894e855..e1814a71 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,7 @@ python:
     - 3.2
     - 3.3
     - 3.4
+    - nightly
     - pypy3
 
 env:
diff --git a/tox.ini b/tox.ini
index 2e227c47..78687ec7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -15,8 +15,8 @@ envlist =
         # Basic configurations: Run the tests in both minimal installations
         # and with all optional dependencies.
         # (pypy3 doesn't have any optional deps yet)
-        {py26,py27,pypy,py32,py33,py34,pypy3},
-        {py26,py27,pypy,py32,py33,py34}-full,
+        {py26,py27,pypy,py32,py33,py34,py35,pypy3},
+        {py26,py27,pypy,py32,py33,py34,py35}-full,
 
         # Also run the tests with each possible replacement of a default
         # component.  Run each test on both python 2 and 3 where possible.
@@ -58,6 +58,7 @@ basepython =
            py32: python3.2
            py33: python3.3
            py34: python3.4
+           py35: python3.5
            pypy: pypy
            pypy3: pypy3
            py2: python2.7
@@ -72,10 +73,10 @@ deps =
      py3-unittest2: unittest2py3k
      # cpython-only deps: pycurl installs but curl_httpclient doesn't work;
      # twisted mostly works but is a bit flaky under pypy.
-     {py26,py27,py32,py33,py34}-full: pycurl
+     {py26,py27,py32,py33,py34,py35}-full: pycurl
      {py2,py3}: pycurl==7.19.3.1
      # twisted is cpython only and doesn't support py32.
-     {py26,py27,py33,py34}-full: twisted
+     {py26,py27,py33,py34,py35}-full: twisted
      {py2,py3}: twisted
      # pycares installation currently fails on py33
      # (https://github.com/pypa/pip/pull/816)
@@ -95,7 +96,7 @@ deps =
 
 setenv =
        # The extension is mandatory on cpython.
-       {py2,py26,py27,py3,py32,py33,py34}: TORNADO_EXTENSION=1
+       {py2,py26,py27,py3,py32,py33,py34,py35}: TORNADO_EXTENSION=1
        # In python 3, opening files in text mode uses a
        # system-dependent encoding by default.  Run the tests with "C"
        # (ascii) and "utf-8" locales to ensure we don't have hidden
@@ -104,7 +105,7 @@ setenv =
        lang_utf8: LANG=en_US.utf-8
        # tox's parser chokes if all the setenv entries are conditional.
        DUMMY=dummy
-       {py2,py26,py27,py3,py32,py33,py34}-no-ext: TORNADO_EXTENSION=0
+       {py2,py26,py27,py3,py32,py33,py34,py35}-no-ext: TORNADO_EXTENSION=0
 
 # All non-comment lines but the last must end in a backslash.
 # Tox filters line-by-line based on the environment name.
@@ -112,7 +113,7 @@ commands =
          python \
          # py3*: -b turns on an extra warning when calling
          # str(bytes), and -bb makes it an error.
-         {py3,py32,py33,py34,pypy3}: -bb \
+         {py3,py32,py33,py34,py35,pypy3}: -bb \
          # Python's optimized mode disables the assert statement, so
          # run the tests in this mode to ensure we haven't fallen into
          # the trap of relying on an assertion's side effects or using