William T. Fauntroy, 79, a retired employe of the Patent Office and a former semiprofessional baseball player, died of cancer Sept. 14 at Howard University Hospital.

Mr. Fauntroy, the father of D.C. Del. Walter E. Fauntroy (D), was a lifelong resident of Washington. He graduated from Dunbar High School. He worked briefly for the Post Office before joining the Patent Office in 1918. He retired in 1962 as a supervisor in the photocopying department.

As a baseball player, Mr. Fauntroy covered center field for the Washington Black Sox, the Le Droit Tigers, the Hillsdales and the Anacostia Aztecs. He also played on two championship softball teams in the city.

Mr. Fauntroy, a former member of the Second Baptist Church, belonged to the New Bethel Baptist Church, of which Del. Fauntroy is the pastor. He was a member of the Usher Board and the Hymnal Club and in 1971 received the church's Father of the Year award.

His wife, the former Ethel Vine, whom he married in 1920, died in 1976.

In addition to Del. Fauntroy, survivors include two daughters, Ellamae F. King and Doris Ann Ball, both of Washington; four other sons, William T. Jr., Kenneth V. and Gerald A., all of Washington, and Raymond C., of Miami, Fla.; 20 grandchildren, and 16 great-grandchildren.