diff --git a/lib/aws_codegen.ex b/lib/aws_codegen.ex
index 8fc0483..91b66bc 100644
--- a/lib/aws_codegen.ex
+++ b/lib/aws_codegen.ex
@@ -26,6 +26,11 @@ defmodule AWS.CodeGen do
               decode: nil,
               encode: nil,
               endpoint_prefix: nil,
+              # Name of the AWS-canonical service-specific endpoint env var
+              # (e.g. "AWS_ENDPOINT_URL_DYNAMODB"). Derived from `service_id`
+              # per the AWS CLI/SDK convention: spaces -> "_", uppercased.
+              # See https://docs.aws.amazon.com/cli/v1/userguide/cli-configure-endpoints.html
+              endpoint_url_env_var: nil,
               is_global: false,
               hostname: nil,
               json_version: nil,
diff --git a/lib/aws_codegen/post_service.ex b/lib/aws_codegen/post_service.ex
index 9a4fb4f..55edf02 100644
--- a/lib/aws_codegen/post_service.ex
+++ b/lib/aws_codegen/post_service.ex
@@ -111,6 +111,7 @@ defmodule AWS.CodeGen.PostService do
       signing_name: signing_name,
       signature_version: AWS.CodeGen.Util.get_signature_version(service),
       service_id: AWS.CodeGen.Util.get_service_id(service),
+      endpoint_url_env_var: "AWS_ENDPOINT_URL_" <> spec.module_name |> String.upcase(),
       target_prefix: target_prefix(spec.api)
     }
   end
diff --git a/lib/aws_codegen/rest_service.ex b/lib/aws_codegen/rest_service.ex
index c9f3795..500a237 100644
--- a/lib/aws_codegen/rest_service.ex
+++ b/lib/aws_codegen/rest_service.ex
@@ -157,6 +157,7 @@ defmodule AWS.CodeGen.RestService do
       signing_name: signing_name,
       signature_version: AWS.CodeGen.Util.get_signature_version(service),
       service_id: AWS.CodeGen.Util.get_service_id(service),
+      endpoint_url_env_var: "AWS_ENDPOINT_URL_" <> spec.module_name |> String.upcase(),
       ## TODO: metadata["targetPrefix"],
       target_prefix: nil,
       shapes: Shapes.collect_shapes(language, spec.api)
diff --git a/priv/post.erl.eex b/priv/post.erl.eex
index 6a42686..544ce52 100644
--- a/priv/post.erl.eex
+++ b/priv/post.erl.eex
@@ -75,8 +75,8 @@ request(Client, Action, Input, Options) ->
 <% else %>do_request(Client, Action, Input0, Options) ->
 <% end %>    Client1 = Client#{service => <<"<%= context.signing_name %>">><%= if context.is_global do %>,
                       region => <<"<%= context.credential_scope %>">><% end %>},
-    Host = build_host(<<"<%= context.endpoint_prefix %>">>, Client1),
-    URL = build_url(Host, Client1),
+    DefaultHost = build_host(<<"<%= context.endpoint_prefix %>">>, Client1),
+    {URL, Host} = aws_util:apply_endpoint_url_override(build_url(DefaultHost, Client1), DefaultHost, <<"/">>, <<"<%= context.endpoint_url_env_var %>">>),
     Headers = [
         {<<"Host">>, Host},
         {<<"Content-Type">>, <<"<%= context.content_type %>">>}<%= if context.protocol == "json" do %>,
diff --git a/priv/rest.erl.eex b/priv/rest.erl.eex
index 251f320..1b4664a 100644
--- a/priv/rest.erl.eex
+++ b/priv/rest.erl.eex
@@ -209,9 +209,11 @@ do_request(Client, Method, Path, Query, Headers0, Input, Options, SuccessStatusC
     Client1 = Client#{service => <<"<%= context.signing_name %>">><%= if context.is_global do %>,
                       region => <<"<%= context.credential_scope %>">><% end %>},
     <%= if context.endpoint_prefix == "s3-control" do %>AccountId = proplists:get_value(<<"x-amz-account-id">>, Headers0),
-    Host = build_host(AccountId, <<"<%= context.endpoint_prefix %>">>, Client1),<% else %><%= if AWS.CodeGen.RestService.Context.s3_context?(context) do %>Host = build_host(<<"<%= context.endpoint_prefix %>">>, Client1, Bucket),<%else %>Host = build_host(<<"<%= context.endpoint_prefix %>">>, Client1),<% end %><% end %>
-    URL0 = build_url(Host, Path, Client1<%= if AWS.CodeGen.RestService.Context.s3_context?(context) do %>, Bucket<% end %>),
-    URL = aws_request:add_query(URL0, Query),
+    DefaultHost = build_host(AccountId, <<"<%= context.endpoint_prefix %>">>, Client1),<% else %><%= if AWS.CodeGen.RestService.Context.s3_context?(context) do %>DefaultHost = build_host(<<"<%= context.endpoint_prefix %>">>, Client1, Bucket),<%else %>DefaultHost = build_host(<<"<%= context.endpoint_prefix %>">>, Client1),<% end %><% end %>
+    URL0 = build_url(DefaultHost, Path, Client1<%= if AWS.CodeGen.RestService.Context.s3_context?(context) do %>, Bucket<% end %>),
+    PathBin = erlang:iolist_to_binary(Path),
+    {URL1, Host} = aws_util:apply_endpoint_url_override(URL0, DefaultHost, PathBin, <<"<%= context.endpoint_url_env_var %>">>),
+    URL = aws_request:add_query(URL1, Query),
     AdditionalHeaders1 = [ {<<"Host">>, Host}
                          , {<<"Content-Type">>, <<"<%= context.content_type %>">>}
                          ],
@@ -332,7 +334,6 @@ build_host(EndpointPrefix, #{endpoint := Endpoint}) ->
     aws_util:binary_join([EndpointPrefix, Endpoint], <<".">>).<% else %>
 build_host(EndpointPrefix, #{region := Region, endpoint := Endpoint}) ->
     aws_util:binary_join([EndpointPrefix, Region, Endpoint], <<".">>).<% end %><% end %><% end %><% end %>
-
 <%= if AWS.CodeGen.RestService.Context.s3_context?(context) do %>build_url(Host0, Path0, Client, Bucket) ->
     Proto = aws_client:proto(Client),
     %% Mocks are notoriously bad with host-style requests, just skip it and use path-style for anything local
diff --git a/test/aws_codegen/rest_service_test.exs b/test/aws_codegen/rest_service_test.exs
index cd45c61..e38a160 100644
--- a/test/aws_codegen/rest_service_test.exs
+++ b/test/aws_codegen/rest_service_test.exs
@@ -51,6 +51,7 @@ defmodule AWS.CodeGen.RestServiceTest do
                module_name: "AWS.CloudTrailData",
                protocol: "rest-json",
                service_id: "CloudTrail Data",
+               endpoint_url_env_var: "AWS_ENDPOINT_URL_CLOUDTRAIL_DATA",
                signature_version: "v4",
                signing_name: "cloudtrail-data",
                target_prefix: nil