RocketMQ

Apache Kafka

apache/kafka

Popular

Distributed event-streaming platform; Kafka 4 removed ZooKeeper in favor of KRaft.

RabbitMQ

rabbitmq/rabbitmq-server

Popular

Mature AMQP message broker with flexible routing, quorum queues and streams.

Amazon SQS

aws.amazon.com

Popular

Fully managed message queue on AWS, the default choice for decoupling services there.

NATS

nats-io/nats-server

Lightweight, high-performance messaging with JetStream persistence, KV and object store.

Redpanda

redpanda-data/redpanda

Kafka API-compatible streaming engine in C++ with no JVM or ZooKeeper.

Apache Pulsar

apache/pulsar

Multi-tenant, geo-replicated messaging and streaming with tiered storage.

Google Cloud Pub/Sub

cloud.google.com

Global, serverless pub/sub messaging service on Google Cloud.

Azure Service Bus

azure.microsoft.com

Enterprise message broker on Azure with queues, topics, sessions and transactions.

Apache ActiveMQ

apache/activemq

Legacy

Veteran JMS message broker (Classic and Artemis) still common in enterprise Java estates.