diff --git a/aws-sdk-core/lib/aws-sdk-core.rb b/aws-sdk-core/lib/aws-sdk-core.rb
index 3bd1f4bdad7..16d67d16ca7 100644
--- a/aws-sdk-core/lib/aws-sdk-core.rb
+++ b/aws-sdk-core/lib/aws-sdk-core.rb
@@ -324,6 +324,7 @@ module Plugins
     autoload :S3RequestSigner, 'aws-sdk-core/plugins/s3_request_signer'
     autoload :S3SseCpk, 'aws-sdk-core/plugins/s3_sse_cpk'
     autoload :S3UrlEncodedKeys, 'aws-sdk-core/plugins/s3_url_encoded_keys'
+    autoload :STSRegionalEndpoints, 'aws-sdk-core/plugins/sts_regional_endpoints'
     autoload :SQSQueueUrls, 'aws-sdk-core/plugins/sqs_queue_urls'
     autoload :SQSMd5s, 'aws-sdk-core/plugins/sqs_md5s'
     autoload :StubResponses, 'aws-sdk-core/plugins/stub_responses'
diff --git a/aws-sdk-core/lib/aws-sdk-core/api/customizations.rb b/aws-sdk-core/lib/aws-sdk-core/api/customizations.rb
index 0cdeafc719f..f53553b7d4d 100644
--- a/aws-sdk-core/lib/aws-sdk-core/api/customizations.rb
+++ b/aws-sdk-core/lib/aws-sdk-core/api/customizations.rb
@@ -274,6 +274,10 @@ def is_eventstream?(api, shape_name)
         Aws::Plugins::S3RequestSigner
       ))
 
+      plugins('AWS Security Token Service', add: %w(
+        Aws::Plugins::STSRegionalEndpoints
+      ))
+
       plugins('AWS S3 Control', add: %w(
         Aws::Plugins::S3HostId
         Aws::Plugins::S3ControlDns
diff --git a/aws-sdk-core/lib/aws-sdk-core/endpoint_provider.rb b/aws-sdk-core/lib/aws-sdk-core/endpoint_provider.rb
index f2f57839329..7f492b297cc 100644
--- a/aws-sdk-core/lib/aws-sdk-core/endpoint_provider.rb
+++ b/aws-sdk-core/lib/aws-sdk-core/endpoint_provider.rb
@@ -2,12 +2,34 @@ module Aws
   # @api private
   class EndpointProvider
 
+    # when sts_regional_endpoint set to `legacy`
+    # endpoint pattern stays global for
+    # following regions
+    STS_LEGACY_REGIONS = %w(
+      ap-northeast-1
+      ap-south-1
+      ap-southeast-1
+      ap-southeast-2
+      aws-global
+      ca-central-1
+      eu-central-1
+      eu-north-1
+      eu-west-1
+      eu-west-2
+      eu-west-3
+      sa-east-1
+      us-east-1
+      us-east-2
+      us-west-1
+      us-west-2
+    )
+
     def initialize(rules)
       @rules = rules
     end
 
-    def resolve(region, service)
-      "https://" + endpoint_for(region, service)
+    def resolve(region, service, sts_regional_endpoints = nil)
+      "https://" + endpoint_for(region, service, sts_regional_endpoints)
     end
 
     def signing_region(region, service)
@@ -27,7 +49,7 @@ def dns_suffix_for(region)
 
     private
 
-    def endpoint_for(region, service)
+    def endpoint_for(region, service, sts_regional_endpoints)
       partition = get_partition(region)
       endpoint = default_endpoint(partition, service, region)
       service_cfg = partition.fetch("services", {}).fetch(service, {})
@@ -35,8 +57,13 @@ def endpoint_for(region, service)
       # Check for service-level default endpoint.
       endpoint = service_cfg.fetch("defaults", {}).fetch("hostname", endpoint)
 
+      # Check for sts legacy behavior
+      sts_legacy = service == 'sts' &&
+        sts_regional_endpoints == 'legacy' &&
+        STS_LEGACY_REGIONS.include?(region)
+
       # Check for global endpoint.
-      if service_cfg["isRegionalized"] == false
+      if sts_legacy || service_cfg["isRegionalized"] == false
         region = service_cfg.fetch("partitionEndpoint", region)
       end
 
@@ -81,8 +108,8 @@ def default_partition
 
     class << self
 
-      def resolve(region, service)
-        default_provider.resolve(region, service)
+      def resolve(region, service, sts_regional_endpoints = nil)
+        default_provider.resolve(region, service, sts_regional_endpoints)
       end
 
       def signing_region(region, service)
diff --git a/aws-sdk-core/lib/aws-sdk-core/plugins/regional_endpoint.rb b/aws-sdk-core/lib/aws-sdk-core/plugins/regional_endpoint.rb
index 9832f931171..c5ff64d8ce8 100644
--- a/aws-sdk-core/lib/aws-sdk-core/plugins/regional_endpoint.rb
+++ b/aws-sdk-core/lib/aws-sdk-core/plugins/regional_endpoint.rb
@@ -26,6 +26,8 @@ class RegionalEndpoint < Seahorse::Client::Plugin
         endpoint_prefix = cfg.api.metadata['endpointPrefix']
         if cfg.region && endpoint_prefix
           EndpointProvider.resolve(cfg.region, endpoint_prefix)
+          sts_regional = cfg.respond_to?(:sts_regional_endpoints) ? cfg.sts_regional_endpoints : nil
+          EndpointProvider.resolve(cfg.region, endpoint_prefix, sts_regional)
         end
       end
 
diff --git a/aws-sdk-core/lib/aws-sdk-core/plugins/sts_regional_endpoints.rb b/aws-sdk-core/lib/aws-sdk-core/plugins/sts_regional_endpoints.rb
new file mode 100644
index 00000000000..231120d60a8
--- /dev/null
+++ b/aws-sdk-core/lib/aws-sdk-core/plugins/sts_regional_endpoints.rb
@@ -0,0 +1,30 @@
+module Aws
+  module Plugins
+
+    class STSRegionalEndpoints < Seahorse::Client::Plugin
+
+      option(:sts_regional_endpoints,
+        default: 'legacy',
+        doc_type: String,
+        docstring: <<-DOCS) do |cfg|
+Passing in 'regional' to enable regional endpoint for STS for all supported
+regions (except 'aws-global'), defaults to 'legacy' mode, using global endpoint
+for legacy regions.
+      DOCS
+        resolve_sts_regional_endpoints(cfg)
+      end
+
+      private
+                                                                       
+      def self.resolve_sts_regional_endpoints(cfg)
+        env_mode = ENV['AWS_STS_REGIONAL_ENDPOINTS']
+        env_mode = nil if env_mode == ''
+        cfg_mode = Aws.shared_config.sts_regional_endpoints(
+          profile: cfg.profile)
+        env_mode || cfg_mode || 'legacy'
+      end
+
+    end
+
+  end
+end
diff --git a/aws-sdk-core/lib/aws-sdk-core/shared_config.rb b/aws-sdk-core/lib/aws-sdk-core/shared_config.rb
index 9239c372a51..71c1cc2d022 100644
--- a/aws-sdk-core/lib/aws-sdk-core/shared_config.rb
+++ b/aws-sdk-core/lib/aws-sdk-core/shared_config.rb
@@ -128,6 +128,21 @@ def region(opts = {})
       end
     end
 
+    def sts_regional_endpoints(opts = {})
+      p = opts[:profile] || @profile_name
+      if @config_enabled
+        if @parsed_credentials
+          mode = @parsed_credentials.fetch(p, {})["sts_regional_endpoints"]
+        end
+        if @parsed_config
+          mode ||= @parsed_config.fetch(p, {})["sts_regional_endpoints"]
+        end
+        mode
+      else
+        nil
+      end
+    end
+
     def endpoint_discovery(opts = {})
       p = opts[:profile] || @profile_name
       if @config_enabled && @parsed_config
diff --git a/aws-sdk-core/spec/aws/shared_config_spec.rb b/aws-sdk-core/spec/aws/shared_config_spec.rb
index 2d866e1ebe7..758baff0c89 100644
--- a/aws-sdk-core/spec/aws/shared_config_spec.rb
+++ b/aws-sdk-core/spec/aws/shared_config_spec.rb
@@ -110,6 +110,26 @@ module Aws
         expect(config.endpoint_discovery).to eq("false")
       end
 
+      context 'sts_regional_endpoints selection' do
+
+        it 'can resolve sts_regional_endpoints from config file' do
+          config = SharedConfig.new(
+            config_path: mock_config_file,
+            config_enabled: true,
+            profile_name: "sts_regional"
+          )
+          expect(config.sts_regional_endpoints).to eq('regional')
+
+          config = SharedConfig.new(
+            config_path: mock_config_file,
+            config_enabled: true,
+            profile_name: "sts_legacy"
+          )
+          expect(config.sts_regional_endpoints).to eq('legacy')
+        end
+
+      end
+
     end
   end
 end
diff --git a/aws-sdk-core/spec/aws/sts/sts_regional_endpoints_spec.rb b/aws-sdk-core/spec/aws/sts/sts_regional_endpoints_spec.rb
new file mode 100644
index 00000000000..074b8be10fa
--- /dev/null
+++ b/aws-sdk-core/spec/aws/sts/sts_regional_endpoints_spec.rb
@@ -0,0 +1,165 @@
+require_relative '../../spec_helper'
+
+module Aws
+  module STS
+    describe Client do
+
+      describe ':sts_regional_endpoints' do
+
+        let(:mock_config_file) {
+          File.expand_path(File.join(File.dirname(__FILE__),
+            '..', 'fixtures', 'credentials', 'mock_shared_config'))
+        }
+
+        it 'uses ENV before shared config' do
+          ENV['AWS_STS_REGIONAL_ENDPOINTS'] = 'regional'
+          config = SharedConfig.new(
+            config_path: mock_config_file,
+            config_enabled: true,
+            profile_name: "sts_legacy"
+          )
+
+          allow(Aws).to receive(:shared_config).and_return(config)
+          client = Client.new(
+            stub_responses: true,
+            region: 'us-west-2'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+        end
+
+        it 'defaults to `legacy`' do
+          client = Client.new(
+            stub_responses: true,
+            region: 'us-west-2'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('legacy')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.amazonaws.com')
+        end
+
+        it 'can be set `regional` in the constructor' do
+          client = Client.new(
+            stub_responses: true,
+            sts_regional_endpoints: 'regional',
+            region: 'us-west-2'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.us-west-2.amazonaws.com')
+        end
+
+        it 'can be set fron ENV' do
+          ENV['AWS_STS_REGIONAL_ENDPOINTS'] = 'regional'
+          client = Client.new(
+            stub_responses: true,
+            region: 'us-west-2'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.us-west-2.amazonaws.com')
+        end
+
+        it 'has no effect on fips endpoint' do
+          client = Client.new(
+            stub_responses: true,
+            region: 'us-west-2-fips'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('legacy')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts-fips.us-west-2.amazonaws.com')
+
+          client = Client.new(
+            stub_responses: true,
+            sts_regional_endpoints: 'regional',
+            region: 'us-west-2-fips'
+          )
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts-fips.us-west-2.amazonaws.com')
+        end
+
+        it 'has no effect on aws-global even when `regional`' do
+          client = Client.new(
+            stub_responses: true,
+            sts_regional_endpoints: 'regional',
+            region: 'aws-global'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.amazonaws.com')
+        end
+
+        it 'has no effect on current regionalized regions' do
+          client = Client.new(
+            stub_responses: true,
+            region: 'ap-east-1'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('legacy')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.ap-east-1.amazonaws.com')
+
+          client = Client.new(
+            stub_responses: true,
+            sts_regional_endpoints: 'regional',
+            region: 'ap-east-1'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.ap-east-1.amazonaws.com')
+        end
+
+        it 'has no effect on cn-north-1 region' do
+          client = Client.new(
+            stub_responses: true,
+            region: 'cn-north-1'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('legacy')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.cn-north-1.amazonaws.com.cn')
+
+          client = Client.new(
+            stub_responses: true,
+            sts_regional_endpoints: 'regional',
+            region: 'cn-north-1'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+          resp = client.get_caller_identity
+          expect(resp.context.http_request.endpoint.to_s).to eq(
+            'https://sts.cn-north-1.amazonaws.com.cn')
+        end
+
+        it 'configures properly at config' do
+          client = Client.new(
+            stub_responses: true,
+            region: 'us-west-2'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('legacy')
+          expect(client.config.region).to eq('us-west-2')
+          expect(client.config.sigv4_region).to eq('us-east-1')
+          expect(client.config.endpoint.to_s).to eq('https://sts.amazonaws.com')
+
+          client = Client.new(
+            stub_responses: true,
+            sts_regional_endpoints: 'regional',
+            region: 'us-west-2'
+          )
+          expect(client.config.sts_regional_endpoints).to eq('regional')
+          expect(client.config.region).to eq('us-west-2')
+          expect(client.config.sigv4_region).to eq('us-west-2')
+          expect(client.config.endpoint.to_s).to eq(
+            'https://sts.us-west-2.amazonaws.com')
+        end
+
+      end
+
+    end
+  end
+end
diff --git a/aws-sdk-core/spec/fixtures/credentials/mock_shared_config b/aws-sdk-core/spec/fixtures/credentials/mock_shared_config
index 57a69ae8c50..e1a4f153aef 100644
--- a/aws-sdk-core/spec/fixtures/credentials/mock_shared_config
+++ b/aws-sdk-core/spec/fixtures/credentials/mock_shared_config
@@ -78,3 +78,13 @@ endpoint_discovery_enabled = true
 aws_access_key_id = AKID
 aws_secret_access_key = SECRET
 endpoint_discovery_enabled = false
+
+[profile sts_regional]
+aws_access_key_id = AKID
+aws_secret_access_key = SECRET
+sts_regional_endpoints = regional
+
+[profile sts_legacy]
+aws_access_key_id = AKID
+aws_secret_access_key = SECRET
+sts_regional_endpoints = legacy