In computing, an agent communication language (ACL) is a formal language used by software agents to communicate.

The most popular ACLs are:

• FIPA-ACL (by the Foundation for Intelligent Physical Agents, a standardization consortium)
• KQML (Knowledge Query and Manipulation Language)

Both rely on speech act theory developed by Searle in 1960 and enhanced by Winograd and Flores in the 70s and define a set of performatives and their meaning (e.g. ask-one). The content of the performative is not standardized, but varies from system to system.

To make agents understand each other they have to not only speak the same language, but also have a common ontology. An ontology is a part of the agent's knowledge base that describes what kind of things an agent can deal with and how they are related to each other. Formal languages | Knowledge representation