A joint session or joint convention is, most broadly, when two normally separate decision-making groups meet, often in a special session or other extraordinary meeting, for a specific purpose.

Most often it refers to when both houses of a bicameral legislature sit together. A joint session typically occurs to receive foreign or domestic diplomats or leaders, or to allow both houses to consider bills together.

Some constitutions give special power to a joint session, voting by majority of all members of the legislature regardless of which house or chamber they belong to. For example, in Switzerland a joint session of the two houses elects the members of the Federal Council (cabinet). In India, disputes between houses are resolved by a joint sitting but without an intervening election.