Harry Maranian, 50, a Fairfax County teacher who was voted Virginia's outstanding social studies teacher for 1979-80, died Thursday at Fairfax Hospital after a heart attack.

Mr. Maranian began as a teacher in Fairfax County elementary schools over 20 years ago and then taught at McLean and Langley high schools. In 1971, he transferred to James W. Robinson Secondary School, where he was chairman of the social studies department.

He developed innovative summer study programs for the county, including institutes on the humanities, an accelerated government course, an environmental studies course and inter-disciplinary programs.

He also taught Asian studies and courses on Russian civilization. He chaperoned eight trips to the Soviet Union for Fairfax County students. He was voted outstanding social studies teacher for the state of Virginia for 1979-80.

Mr. Maranian was born and reared in Washington. He earned bachelor's and master's degree in political science and history from American University.

A resident of Vienna, he was active in Our Lady of Lady of Good Counsel Catholic Church there and was a member of the parish council and a leader of church youth groups.

Survivors include his mother, Margaret Maranian of Vienna; a brother Peter, of Gloucester, Mass., and two sisters, Marian Barsom of Whittier, Calif., and Helen, of Lincoln, Mass.

The family suggests that expressions of sympathy be in the form of contributions to the Northern Virginia Heart Fund, the Hospice of Northern Virginia or to the Maranian Memorial Fund at Robinson Secondary School.