diff --git a/Sources/Kafka/ForTesting/RDKafkaClient+Group.swift b/Sources/Kafka/ForTesting/RDKafkaClient+Group.swift
new file mode 100644
index 00000000..418e3ced
--- /dev/null
+++ b/Sources/Kafka/ForTesting/RDKafkaClient+Group.swift
@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the swift-kafka-client open source project
+//
+// Copyright (c) 2022 Apple Inc. and the swift-kafka-client project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of swift-kafka-client project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Crdkafka
+import Logging
+
+@_spi(Internal)
+extension RDKafkaClient {
+    /// List client consumer groups in cluster.
+    /// Blocks for a maximum of `timeout` milliseconds.
+    /// - Parameter timeout: timeout
+    /// - Returns: Groups
+    /// - Throws: A ``KafkaError`` if kafka call fails.
+    public func _listGroups(timeout: Duration) throws -> [KafkaGroup] {
+        try withKafkaHandlePointer { kafkaHandle in
+            var adminOptions = rd_kafka_AdminOptions_new(kafkaHandle, RD_KAFKA_ADMIN_OP_LISTCONSUMERGROUPS)
+            defer { rd_kafka_AdminOptions_destroy(adminOptions) }
+
+            let timeoutMs = Int32(timeout.inMilliseconds)
+            if timeoutMs > 0 {
+                let errorChars = UnsafeMutablePointer<CChar>.allocate(capacity: RDKafkaClient.stringSize)
+                defer { errorChars.deallocate() }
+                let err = rd_kafka_AdminOptions_set_request_timeout(adminOptions, timeoutMs, errorChars, RDKafkaClient.stringSize)
+                if err != RD_KAFKA_RESP_ERR_NO_ERROR {
+                    throw KafkaError.rdKafkaError(wrapping: err, errorMessage: String(cString: errorChars))
+                }
+            }
+
+            let resultQueue = rd_kafka_queue_new(kafkaHandle)
+            defer { rd_kafka_queue_destroy(resultQueue) }
+
+            rd_kafka_ListConsumerGroups(kafkaHandle, adminOptions, resultQueue)
+
+            guard let resultEvent = rd_kafka_queue_poll(resultQueue, timeoutMs) else {
+                throw KafkaError.rdKafkaError(errorMessage: "rd_kafka_queue_poll() timed out")
+            }
+            defer { rd_kafka_event_destroy(resultEvent) }
+
+            if rd_kafka_event_error(resultEvent) != RD_KAFKA_RESP_ERR_NO_ERROR {
+                let errorMessage = String(cString: rd_kafka_event_error_string(resultEvent))
+                throw KafkaError.rdKafkaError(wrapping: rd_kafka_event_error(resultEvent), errorMessage: errorMessage)
+            }
+
+            let result = rd_kafka_event_ListConsumerGroups_result(resultEvent)
+
+            var groupsCnt: size_t = 0
+            let groups = rd_kafka_ListConsumerGroups_result_valid(result, &groupsCnt)
+            guard let groups else {
+                return []
+            }
+
+            var ret = [KafkaGroup]()
+            for idx in 0..<groupsCnt {
+                let group = groups[idx]
+                let groupId = rd_kafka_ConsumerGroupListing_group_id(group)
+                guard let groupId else {
+                    throw KafkaError.rdKafkaError(errorMessage: "rd_kafka_ConsumerGroupListing_group_id() unexpectedly returned nil")
+                }
+                let kafkaGroupState = rd_kafka_ConsumerGroupListing_state(group)
+                guard let state = KafkaGroup.State(rawValue: kafkaGroupState.rawValue) else {
+                    throw KafkaError.rdKafkaError(errorMessage: "unexpected value \(kafkaGroupState) for rd_kafka_consumer_group_state_t enumeration")
+                }
+                let isSimple = rd_kafka_ConsumerGroupListing_is_simple_consumer_group(group)
+                let kafkaGroup = KafkaGroup(name: String(cString: groupId), state: state, isSimple: isSimple != 0)
+                ret.append(kafkaGroup)
+            }
+
+            return ret
+        }
+    }
+}
diff --git a/Sources/Kafka/KafkaError.swift b/Sources/Kafka/KafkaError.swift
index 07978168..8afdcf4f 100644
--- a/Sources/Kafka/KafkaError.swift
+++ b/Sources/Kafka/KafkaError.swift
@@ -70,6 +70,27 @@ public struct KafkaError: Error, CustomStringConvertible, @unchecked Sendable {
         )
     }
 
+    static func rdKafkaError(
+        wrapping error: rd_kafka_resp_err_t, errorMessage: String, isFatal: Bool = false, file: String = #fileID, line: UInt = #line
+    ) -> KafkaError {
+        let errorMessage = String(cString: rd_kafka_err2str(error)) + ": " + errorMessage
+        return KafkaError(
+            backing: .init(
+                code: .underlying, reason: errorMessage, file: file, line: line
+            )
+        )
+    }
+
+    static func rdKafkaError(
+        errorMessage: String, isFatal: Bool = false, file: String = #fileID, line: UInt = #line
+    ) -> KafkaError {
+        return KafkaError(
+            backing: .init(
+                code: .underlying, reason: errorMessage, file: file, line: line
+            )
+        )
+    }
+
     static func config(
         reason: String, file: String = #fileID, line: UInt = #line
     ) -> KafkaError {
diff --git a/Sources/Kafka/KafkaGroup.swift b/Sources/Kafka/KafkaGroup.swift
new file mode 100644
index 00000000..3f42d6e8
--- /dev/null
+++ b/Sources/Kafka/KafkaGroup.swift
@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the swift-kafka-client open source project
+//
+// Copyright (c) 2023 Apple Inc. and the swift-kafka-client project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of swift-kafka-client project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Crdkafka
+
+public struct KafkaGroup {
+    /// Swift `enum` wrapping `librdkafka`'s `RD_KAFKA_CONSUMER_GROUP_STATE_*` values.
+    /// See `rd_kafka_consumer_group_state_t` in rdkafka.h for reference.
+    public enum State: UInt32 {
+        case unknown = 0
+        case preparingRebalance = 1
+        case completingRebalance = 2
+        case stable = 3
+        case dead = 4
+        case empty = 5
+    }
+
+    public let name: String
+    public let state: State
+    public let isSimple: Bool
+}