In government, bicameralism is the practice of having two legislative or parliamentary chambers. Thus, a bicameral parliament or bicameral legislature is a parliament or legislature which consists of two chambers or Houses.

The relationship between the two chambers varies; in some cases, they have equal power, while in others, one chamber is clearly superior to the other. It is also commonplace in most federal systems to have a bicameral legislature, with the second chamber representing the constitutent states, such as the United States Senate.

Some political scientists believe that bicameralism makes meaningful political reforms more difficult to achieve and increases the risk of deadlock. This risk of deadlock is greater in cases where both chambers have equal powers. Others argue strongly for the merits of the 'checks and balances' provided by the bicameral model, which they believe helps prevent ill-considered legislation from being passed into law.

Notes: in the United States all of the state legislatures except Nebraska's are also bicameral. In Australia all of the state parliaments except Queensland's are also bicameral.