Parliamentary elections were held in Sri Lanka on 21 July 1977. The result was a landslide victory for the United National Party, which won 140 of the 168 seats in the National State Assembly.

The United National Party is a centre-right political party in Sri Lanka. The UNP has served as the country's ruling party, or as part of its governing coalition, for 38 of the country's 74 years of independence, including the periods 1947–1956, 1965–1970, 1977–1994, 2001–2004 and 2015–2019. The party also controlled the executive presidency from its formation in 1978 until 1994 and back in 2022.