The Triennial Act, of 1641, was a piece of legislation passed by the English Long Parliament, during the reign of King Charles I. The act requires that the Parliament meet for at least a fifty-day session once every three years. It was intended to prevent Kings from ruling without Parliament, as had been done between 1629 and 1640. In 1664, it was repealed.

Triennial Act, of 1694 Parliament met annually and held general elections once every three years. The country now remained in a grip of constant election fever (10 elections in 20 years) and loyalties among MPs were difficult to establish. This increased faction and rivalry. In 1716 the Septennial Act was created, under which a parliament could remain in being for seven years.