diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c27c85f..ee5230a1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### New Features
 
+* [#887](https://github.com/toptal/chewy/pull/887): Add support [runtime_mappings](https://www.elastic.co/guide/en/elasticsearch/reference/current/runtime-search-request.html). ([@TakuyaKurimoto](https://github.com/TakuyaKurimoto))
 ### Changes
 
 ### Bugs Fixed
diff --git a/README.md b/README.md
index 096bdb57..55e7bc91 100644
--- a/README.md
+++ b/README.md
@@ -1171,6 +1171,23 @@ scope.each do |wrapper|
 end
 ```
 
+#### runtime_mappings
+
+You can define runtime fields in a search request as described [here](https://www.elastic.co/guide/en/elasticsearch/reference/current/runtime-search-request.html):
+
+```ruby
+CitiesIndex
+  .runtime_mappings(
+    field1: {
+      type: 'keyword',
+      :script=>{
+        :lang=>"painless",
+        :source=>"emit('some script here')"
+      }
+    }
+  )
+```
+
 ### Rake tasks
 
 For a Rails application, some index-maintaining rake tasks are defined.
diff --git a/lib/chewy/search/parameters/runtime_mappings.rb b/lib/chewy/search/parameters/runtime_mappings.rb
new file mode 100644
index 00000000..b60a09a6
--- /dev/null
+++ b/lib/chewy/search/parameters/runtime_mappings.rb
@@ -0,0 +1,14 @@
+module Chewy
+  module Search
+    class Parameters
+      # Just a standard hash storage. Nothing to see here.
+      #
+      # @see Chewy::Search::Parameters::HashStorage
+      # @see Chewy::Search::Request#runtime_mappings
+      # @see https://www.elastic.co/guide/en/elasticsearch/reference/current/runtime-search-request.html
+      class RuntimeMappings < Storage
+        include HashStorage
+      end
+    end
+  end
+end
diff --git a/lib/chewy/search/request.rb b/lib/chewy/search/request.rb
index 27d5cdef..1254888a 100644
--- a/lib/chewy/search/request.rb
+++ b/lib/chewy/search/request.rb
@@ -25,7 +25,7 @@ class Request
         search_type preference limit offset terminate_after
         timeout min_score source stored_fields search_after
         load script_fields suggest aggs aggregations collapse none
-        indices_boost rescore highlight total total_count
+        indices_boost rescore highlight runtime_mappings total total_count
         total_entries indices types delete_all count exists?
         exist? find pluck scroll_batches scroll_hits
         scroll_results scroll_wrappers ignore_unavailable
@@ -656,7 +656,23 @@ def load(options = nil)
       #   @see https://www.elastic.co/guide/en/elasticsearch/reference/current/highlighting.html
       #   @param value [Hash]
       #   @return [Chewy::Search::Request]
-      %i[script_fields indices_boost rescore highlight].each do |name|
+      #
+      # @!method runtime_mappings(value)
+      #   Add a `runtime_mappings` part to the request. Further
+      #   call values are merged to the storage hash.
+      #
+      #   @example
+      #     PlacesIndex
+      #       .runtime_mappings(field1: {type: "keyword", :script=>{:lang=>"painless", :source=>"emit('some script here')"}})
+      #       .runtime_mappings(field2: {type: "keyword", :script=>{:lang=>"painless", :source=>"emit('some script here')"}})
+      #     # => <PlacesIndex::Query {..., :body=>{:runtime_mappings=>{
+      #     #      "field1"=>{:type=>"keyword", :script=>{:lang=>"painless", :source=>"emit('some script here')"}},
+      #     #      "field2"=>{:type=>"keyword", :script=>{:lang=>"painless", :source=>"emit('some script here')"}}}}}>
+      #   @see Chewy::Search::Parameters::ScriptFields
+      #   @see https://www.elastic.co/guide/en/elasticsearch/reference/current/runtime-search-request.html
+      #   @param value [Hash]
+      #   @return [Chewy::Search::Request]
+      %i[script_fields indices_boost rescore highlight runtime_mappings].each do |name|
         define_method name do |value|
           modify(name) { update!(value) }
         end
diff --git a/spec/chewy/search/parameters/runtime_mappings_spec.rb b/spec/chewy/search/parameters/runtime_mappings_spec.rb
new file mode 100644
index 00000000..f3334739
--- /dev/null
+++ b/spec/chewy/search/parameters/runtime_mappings_spec.rb
@@ -0,0 +1,5 @@
+require 'chewy/search/parameters/hash_storage_examples'
+
+describe Chewy::Search::Parameters::RuntimeMappings do
+  it_behaves_like :hash_storage, :runtime_mappings
+end
diff --git a/spec/chewy/search/request_spec.rb b/spec/chewy/search/request_spec.rb
index b73b9916..af004bac 100644
--- a/spec/chewy/search/request_spec.rb
+++ b/spec/chewy/search/request_spec.rb
@@ -284,7 +284,7 @@
     specify { expect { subject.stored_fields(:foo) }.not_to change { subject.render } }
   end
 
-  %i[script_fields highlight].each do |name|
+  %i[script_fields highlight runtime_mappings].each do |name|
     describe "##{name}" do
       specify { expect(subject.send(name, foo: {bar: 42}).render[:body]).to include(name => {'foo' => {bar: 42}}) }
       specify do