diff --git a/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h b/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h
index 203022fa2253..b6072387f984 100644
--- a/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h
+++ b/src/aws-cpp-sdk-core/include/aws/core/client/ClientConfiguration.h
@@ -362,6 +362,16 @@ namespace Aws
              */
             bool disableExpectHeader = false;
 
+            /**
+             * Only works for Curl http client.
+             * Sets the timeout in milliseconds that Curl will wait for a 100-Continue response from the server
+             * before sending the request body. This corresponds to CURLOPT_EXPECT_100_TIMEOUT_MS.
+             * Useful when operating behind proxies that introduce network delays, where the default 1000ms
+             * may be too short and cause IncompleteBody errors.
+             * Default 1000ms (Curl's built-in default).
+             */
+            long expect100ContinueTimeoutMs = 1000;
+
             /**
              * If set to true clock skew will be adjusted after each http attempt, default to true.
              */
diff --git a/src/aws-cpp-sdk-core/include/aws/core/http/curl/CurlHandleContainer.h b/src/aws-cpp-sdk-core/include/aws/core/http/curl/CurlHandleContainer.h
index 3ce921b57db1..328b9947430b 100644
--- a/src/aws-cpp-sdk-core/include/aws/core/http/curl/CurlHandleContainer.h
+++ b/src/aws-cpp-sdk-core/include/aws/core/http/curl/CurlHandleContainer.h
@@ -31,7 +31,7 @@ class CurlHandleContainer
       */
     CurlHandleContainer(unsigned maxSize = 50, long httpRequestTimeout = 0, long connectTimeout = 1000, bool tcpKeepAlive = true,
                         unsigned long tcpKeepAliveIntervalMs = 30000, long lowSpeedTime = 3000, unsigned long lowSpeedLimit = 1,
-                        Version version = Version::HTTP_VERSION_2TLS);
+                        Version version = Version::HTTP_VERSION_2TLS, long expect100ContinueTimeoutMs = 1000);
     ~CurlHandleContainer();
 
     /**
@@ -71,6 +71,7 @@ class CurlHandleContainer
     unsigned m_poolSize;
     std::mutex m_containerLock;
     Version m_version;
+    long m_expect100ContinueTimeoutMs;
 };
 
 } // namespace Http
diff --git a/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp b/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp
index cc805c69eb99..f793bb5d49df 100644
--- a/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp
+++ b/src/aws-cpp-sdk-core/source/client/ClientConfiguration.cpp
@@ -247,6 +247,7 @@ void setLegacyClientConfigurationParameters(ClientConfiguration& clientConfig)
     clientConfig.httpClientChunkedMode = HttpClientChunkedMode::CLIENT_IMPLEMENTATION;
     clientConfig.followRedirects = FollowRedirectsPolicy::DEFAULT;
     clientConfig.disableExpectHeader = false;
+    clientConfig.expect100ContinueTimeoutMs = 1000;
     clientConfig.enableClockSkewAdjustment = true;
     clientConfig.enableHostPrefixInjection = true;
     clientConfig.enableHttpClientTrace = false;
diff --git a/src/aws-cpp-sdk-core/source/http/curl/CurlHandleContainer.cpp b/src/aws-cpp-sdk-core/source/http/curl/CurlHandleContainer.cpp
index edc410a4ee67..bb70f86248c2 100644
--- a/src/aws-cpp-sdk-core/source/http/curl/CurlHandleContainer.cpp
+++ b/src/aws-cpp-sdk-core/source/http/curl/CurlHandleContainer.cpp
@@ -16,10 +16,10 @@ static const char* CURL_HANDLE_CONTAINER_TAG = "CurlHandleContainer";
 
 CurlHandleContainer::CurlHandleContainer(unsigned maxSize, long httpRequestTimeout, long connectTimeout, bool enableTcpKeepAlive,
                                         unsigned long tcpKeepAliveIntervalMs, long lowSpeedTime, unsigned long lowSpeedLimit,
-                                        Version version) :
+                                        Version version, long expect100ContinueTimeoutMs) :
                 m_maxPoolSize(maxSize), m_httpRequestTimeout(httpRequestTimeout), m_connectTimeout(connectTimeout), m_enableTcpKeepAlive(enableTcpKeepAlive),
                 m_tcpKeepAliveIntervalMs(tcpKeepAliveIntervalMs), m_lowSpeedTime(lowSpeedTime), m_lowSpeedLimit(lowSpeedLimit), m_poolSize(0),
-                m_version(version)
+                m_version(version), m_expect100ContinueTimeoutMs(expect100ContinueTimeoutMs)
 {
     AWS_LOGSTREAM_INFO(CURL_HANDLE_CONTAINER_TAG, "Initializing CurlHandleContainer with size " << maxSize);
 }
@@ -174,6 +174,7 @@ void CurlHandleContainer::SetDefaultOptionsOnHandle(CURL* handle)
     curl_easy_setopt(handle, CURLOPT_TCP_KEEPIDLE, m_tcpKeepAliveIntervalMs / 1000);
     curl_easy_setopt(handle, CURLOPT_HTTP_VERSION, ConvertHttpVersion(m_version));
     curl_easy_setopt(handle, CURLOPT_MAXCONNECTS, m_maxPoolSize);
+    curl_easy_setopt(handle, CURLOPT_EXPECT_100_TIMEOUT_MS, m_expect100ContinueTimeoutMs);
 }
 
 long CurlHandleContainer::ConvertHttpVersion(Version version) {
diff --git a/src/aws-cpp-sdk-core/source/http/curl/CurlHttpClient.cpp b/src/aws-cpp-sdk-core/source/http/curl/CurlHttpClient.cpp
index 58fc56875de7..a2df8714f137 100644
--- a/src/aws-cpp-sdk-core/source/http/curl/CurlHttpClient.cpp
+++ b/src/aws-cpp-sdk-core/source/http/curl/CurlHttpClient.cpp
@@ -602,7 +602,8 @@ const bool FORCE_ENABLE_CURL_LOGGING = false;
 CurlHttpClient::CurlHttpClient(const ClientConfiguration& clientConfig) :
     Base(),
     m_curlHandleContainer(clientConfig.maxConnections, clientConfig.httpRequestTimeoutMs, clientConfig.connectTimeoutMs, clientConfig.enableTcpKeepAlive,
-                          clientConfig.tcpKeepAliveIntervalMs, clientConfig.requestTimeoutMs, clientConfig.lowSpeedLimit, clientConfig.version),
+                          clientConfig.tcpKeepAliveIntervalMs, clientConfig.requestTimeoutMs, clientConfig.lowSpeedLimit, clientConfig.version,
+                          clientConfig.expect100ContinueTimeoutMs),
     m_isAllowSystemProxy(clientConfig.allowSystemProxy), m_isUsingProxy(!clientConfig.proxyHost.empty()), m_proxyUserName(clientConfig.proxyUserName),
     m_proxyPassword(clientConfig.proxyPassword), m_proxyScheme(SchemeMapper::ToString(clientConfig.proxyScheme)), m_proxyHost(clientConfig.proxyHost),
     m_proxySSLCertPath(clientConfig.proxySSLCertPath), m_proxySSLCertType(clientConfig.proxySSLCertType),