Robert S. Hope, 56, a Washington attorney and former government official who had been active in Republican Party politics in Northern Virginia, died Friday at Suburban Hospital after a stroke.

Mr. Hope was vice chairman and then chairman of the Alexandria Republican City Committee in the mid-1950s. He was a member of the Republican State Central Committee in 1964 when he cochaired the Northern Virginia Republicans for L.B.J.

He came to Washington after World War II and maintained a private law practice, specializing in maritime law, before joining the government in 1969. For the next seven years he worked as a confidential assistant and then as a managing director at the Federal Maritime Commission.He left the Commission to join the Washington law firm of Alvord and Alvord in 1976.

He was a member of the District of Columbia and Virginia bar associations, the Maritime Law Association of the United States, and the Maritime Administrative Bar Association.

Mr. Hope was a native of Garden City, Kan., and a graduate of the U.S. Merchant Marine Academy. He was an officer in the merchant marine during World War II.

He earned both bachelor's and law degrees at George Washington University. He was a former resident of Alexandria. He lived in Damascus, Md., at the time of his death.

Mr. Hope's first marriage ended in divorce.

His survivors include his wife, Adrienne G., of Damascus; two daughters, Alison Hope of Chicago, and Jenifer Hope of Beloit, Wis.; two step-children, Gilbert and Anita Guiliani, both of Damascus; his mother, Mrs. Joe H. Hope of Kansas, and two brothers.

The family suggests that expressions of sympathy be in the form of contributions to the Heart or Lung Associations.