diff --git a/.travis.yml b/.travis.yml
index 3a3f7aac3..619284ed7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -117,3 +117,5 @@ script:
   - python test/component_failures_test.py
   - python test/multi_node_test.py
   - python test/recursion_test.py
+
+  - python -m pytest python/ray/rllib/test/test_catalog.py
diff --git a/.travis/install-dependencies.sh b/.travis/install-dependencies.sh
index 2d056de9a..cba8a1a47 100755
--- a/.travis/install-dependencies.sh
+++ b/.travis/install-dependencies.sh
@@ -24,7 +24,7 @@ if [[ "$PYTHON" == "2.7" ]] && [[ "$platform" == "linux" ]]; then
   wget https://repo.continuum.io/miniconda/Miniconda2-latest-Linux-x86_64.sh -O miniconda.sh
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
-  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow flatbuffers
+  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow gym flatbuffers
 elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "linux" ]]; then
   sudo apt-get update
   sudo apt-get install -y cmake pkg-config python-dev python-numpy build-essential autoconf curl libtool libboost-dev libboost-filesystem-dev libboost-system-dev unzip
@@ -32,7 +32,7 @@ elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "linux" ]]; then
   wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
-  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow flatbuffers
+  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow gym flatbuffers
 elif [[ "$PYTHON" == "2.7" ]] && [[ "$platform" == "macosx" ]]; then
   # check that brew is installed
   which -s brew
@@ -48,7 +48,7 @@ elif [[ "$PYTHON" == "2.7" ]] && [[ "$platform" == "macosx" ]]; then
   wget https://repo.continuum.io/miniconda/Miniconda2-latest-MacOSX-x86_64.sh -O miniconda.sh
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
-  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow flatbuffers
+  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow gym flatbuffers
 elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "macosx" ]]; then
   # check that brew is installed
   which -s brew
@@ -64,7 +64,7 @@ elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "macosx" ]]; then
   wget https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh -O miniconda.sh
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
-  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow flatbuffers
+  pip install numpy cloudpickle==0.3.0 cython cmake funcsigs click colorama psutil redis tensorflow gym flatbuffers
 elif [[ "$LINT" == "1" ]]; then
   sudo apt-get update
   sudo apt-get install -y cmake build-essential autoconf curl libtool libboost-dev libboost-filesystem-dev libboost-system-dev unzip
diff --git a/python/ray/rllib/models/catalog.py b/python/ray/rllib/models/catalog.py
index ec1332747..f5df8100b 100644
--- a/python/ray/rllib/models/catalog.py
+++ b/python/ray/rllib/models/catalog.py
@@ -32,6 +32,8 @@ class ModelCatalog(object):
         action_op = dist.sample()
     """
 
+    _registered_preprocessor = dict()
+
     @staticmethod
     def get_action_dist(action_space, dist_type=None):
         """Returns action distribution class and size for the given action space.
@@ -76,8 +78,8 @@ class ModelCatalog(object):
 
         return FullyConnectedNetwork(inputs, num_outputs, options)
 
-    @staticmethod
-    def get_preprocessor(env_name, obs_shape, options=dict()):
+    @classmethod
+    def get_preprocessor(cls, env_name, obs_shape, options=dict()):
         """Returns a suitable processor for the given environment.
 
         Args:
@@ -97,6 +99,9 @@ class ModelCatalog(object):
                     "Unknown config key `{}`, all keys: {}".format(
                         k, MODEL_CONFIGS))
 
+        if env_name in cls._registered_preprocessor:
+            return cls._registered_preprocessor[env_name](options)
+
         if obs_shape == ATARI_OBS_SHAPE:
             print("Assuming Atari pixel env, using AtariPixelPreprocessor.")
             return AtariPixelPreprocessor(options)
@@ -106,3 +111,15 @@ class ModelCatalog(object):
 
         print("Non-atari env, not using any observation preprocessor.")
         return NoPreprocessor(options)
+
+    @classmethod
+    def register_preprocessor(cls, env_name, preprocessor_class):
+        """Register a preprocessor class for a specific environment.
+
+        Args:
+            env_name (str): Name of the gym env we register the
+                preprocessor for.
+            preprocessor_class (type):
+                Python class of the distribution.
+        """
+        cls._registered_preprocessor[env_name] = preprocessor_class
diff --git a/python/ray/rllib/test/test_catalog.py b/python/ray/rllib/test/test_catalog.py
new file mode 100644
index 000000000..e229e2616
--- /dev/null
+++ b/python/ray/rllib/test/test_catalog.py
@@ -0,0 +1,14 @@
+from ray.rllib.models import ModelCatalog
+from ray.rllib.models.preprocessors import Preprocessor
+
+
+class FakePreprocessor(Preprocessor):
+
+    def __init__(self, options):
+        pass
+
+
+def test_preprocessor():
+    ModelCatalog.register_preprocessor("FakeEnv-v0", FakePreprocessor)
+    preprocessor = ModelCatalog.get_preprocessor("FakeEnv-v0", (1, 1))
+    assert type(preprocessor) == FakePreprocessor
diff --git a/python/setup.py b/python/setup.py
index 2684b55be..49533a8ef 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -86,6 +86,7 @@ setup(name="ray",
                         "click",
                         "colorama",
                         "psutil",
+                        "pytest",
                         "redis",
                         "cloudpickle >= 0.2.2",
                         # The six module is required by pyarrow.