The Presidium or Praesidium (from Latin praesidium meaning protection or defense so plural presidia or praesidia) is the name for the executive committee of various legislative and organizational bodies.
In Communist states the presidium was the permanent executive committee of legislative bodies such as the Supreme Soviet in the USSR. The Presidium of the Supreme Soviet of the USSR existed since 1936 when the Supreme Soviet replaced the Central Executive Committee, and from 1936 until 1991 the Chairman of the Presidium of the Supreme Soviet was the formal title of the President of the Soviet Union.
From 1952 to 1966 the Politburo of the Communist Party of the Soviet Union was known as the Presidium of the Communist Party but despite the similarity in name, the two Presidia were different bodies with different functions.
A praesidium is the group of people that take care of the daily management of a student organisation in Flanders.