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diff --git a/tensorflow/core/grappler/optimizers/data/map_fusion.cc b/tensorflow/core/grappler/optimizers/data/map_fusion.cc
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+++ b/tensorflow/core/grappler/optimizers/data/map_fusion.cc
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+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/core/grappler/optimizers/data/map_fusion.h"
+
+#include "tensorflow/core/framework/attr_value.pb.h"
+#include "tensorflow/core/framework/node_def.pb.h"
+#include "tensorflow/core/grappler/clusters/cluster.h"
+#include "tensorflow/core/grappler/grappler_item.h"
+#include "tensorflow/core/grappler/mutable_graph_view.h"
+#include "tensorflow/core/grappler/op_types.h"
+#include "tensorflow/core/grappler/optimizers/custom_graph_optimizer_registry.h"
+#include "tensorflow/core/grappler/optimizers/data/fusion_utils.h"
+#include "tensorflow/core/grappler/optimizers/data/graph_utils.h"
+#include "tensorflow/core/grappler/utils.h"
+#include "tensorflow/core/grappler/utils/topological_sort.h"
+#include "tensorflow/core/platform/protobuf.h"
+
+namespace tensorflow {
+namespace grappler {
+namespace {
+
+// Sets basic function parameters and copies attributes from parent and map
+// node.
+NodeDef MakeFusedNode(const NodeDef& parent_map_node, const NodeDef& map_node,
+                      const FunctionDef& fused_function,
+                      MutableGraphView* graph) {
+  NodeDef fused_node;
+  graph_utils::SetUniqueGraphNodeName("fused_map", graph->GetGraph(),
+                                      &fused_node);
+
+  fused_node.set_op("MapDataset");
+  fused_node.add_input(parent_map_node.input(0));
+
+  auto copy_attribute = [](const string& attribute_name, const NodeDef& from,
+                           NodeDef* to) {
+    (*to->mutable_attr())[attribute_name] = from.attr().at(attribute_name);
+  };
+
+  auto attr = parent_map_node.attr().at("f");
+  *attr.mutable_func()->mutable_name() = fused_function.signature().name();
+  (*fused_node.mutable_attr())["f"] = std::move(attr);
+
+  copy_attribute("Targuments", parent_map_node, &fused_node);
+
+  for (auto key : {"output_shapes", "output_types"})
+    copy_attribute(key, map_node, &fused_node);
+
+  return fused_node;
+}
+
+}  // namespace
+
+Status MapFusion::Optimize(Cluster* cluster, const GrapplerItem& item,
+                           GraphDef* output) {
+  GraphDef sorted_old_graph = item.graph;
+  TF_RETURN_IF_ERROR(TopologicalSort(&sorted_old_graph));
+  *output = sorted_old_graph;
+
+  MutableGraphView graph(output);
+  std::set<string> nodes_to_delete;
+  FunctionLibraryDefinition function_library(OpRegistry::Global(),
+                                             item.graph.library());
+
+  auto get_map_node = [](const NodeDef& node) -> const NodeDef* {
+    // TODO(prazek): we could also handle ParallelMapDataset and
+    // MapAndBatchDataset.
+    if (node.op() == "MapDataset") return &node;
+    return nullptr;
+  };
+
+  auto get_fused_function = [&function_library, &output](
+                                const NodeDef* parent_map_node,
+                                const NodeDef* map_node) -> FunctionDef* {
+    const auto& parent_fun = parent_map_node->attr().at("f");
+    const FunctionDef* parent_func =
+        function_library.Find(parent_fun.func().name());
+    const auto& fun = map_node->attr().at("f");
+    const FunctionDef* func = function_library.Find(fun.func().name());
+
+    if (!fusion_utils::CanCompose(parent_func->signature(), func->signature()))
+      return nullptr;
+    return fusion_utils::FuseFunctions(
+        *parent_func, *func, "fused_map", fusion_utils::ComposeSignature,
+        fusion_utils::ComposeInput, fusion_utils::ComposeOutput,
+        output->mutable_library());
+  };
+
+  for (const NodeDef& node : sorted_old_graph.node()) {
+    const NodeDef* map_node = get_map_node(node);
+    if (!map_node) continue;
+
+    GraphView::InputPort input_port = graph.GetInputPort(map_node->name(), 0);
+    const NodeDef* parent_map_node =
+        get_map_node(*graph.GetRegularFanin(input_port).node);
+    if (!parent_map_node) continue;
+
+    const auto* fused_function = get_fused_function(parent_map_node, map_node);
+    if (fused_function == nullptr) continue;
+    const auto* fused_maps_node = graph.AddNode(
+        MakeFusedNode(*parent_map_node, *map_node, *fused_function, &graph));
+
+    graph.ReplaceInput(*map_node, *fused_maps_node);
+
+    // TODO(prazek): we should run some optimizations on the fused map
+    // functions, or make sure that optimization passes run after map
+    // fusion.
+    TF_RETURN_IF_ERROR(function_library.AddFunctionDef(*fused_function));
+
+    // TODO(prazek): we could also remove map functions from library if they
+    // are not used anymore.
+    nodes_to_delete.insert(parent_map_node->name());
+    nodes_to_delete.insert(map_node->name());
+  }
+
+  graph.DeleteNodes(nodes_to_delete);
+  return Status::OK();
+}
+
+void MapFusion::Feedback(Cluster* cluster, const GrapplerItem& item,
+                         const GraphDef& optimize_output, double result) {
+  // no-op
+}
+
+REGISTER_GRAPH_OPTIMIZER_AS(MapFusion, "map_fusion");
+
+}  // end namespace grappler
+}  // end namespace tensorflow