A senate is a deliberative assembly, often the upper house or chamber of a bicameral legislature. The name comes from the ancient Roman Senate (Latin: Senatus), so-called as an assembly of the senior (Latin: senex meaning "the elder" or "old man") and therefore considered wiser and more experienced members of the society or ruling class. However the Roman Senate was not the ancestor or predecessor of modern parliamentarism in any sense, because the Roman senate was not a de jure legislative body.

Many countries have an assembly named a senate, composed of senators who may be elected, appointed, have inherited the title, or gained membership by other methods, depending on the country. Modern senates typically serve to provide a chamber of "sober second thought" to consider legislation passed by a lower house, whose members are usually elected. Most senates have asymmetrical duties and powers compared with their respective lower house meaning they have special duties, for example to fill important political positions or to pass special laws. Conversely many senates have limited powers in changing or stopping bills under consideration and efforts to stall or veto a bill may be bypassed by the lower house or another branch of government.