Robert Hanson Harrison (1745 – April 2, 1790) was an American jurist.
Harrison began the American Revolutionary War as a lieutenant in the 3rd Virginia Regiment of the Continental Army. In 1775 he became an aide-de-camp to General George Washington with the rank of lieutenant colonel. The next year he succeeded Joseph Reed as military secretary to Washington, and served in that role until 1781. Prior to the war Harrison was Washington’s chief lawyer.
He served as a judge in Maryland from 1781 to 1789, but he declined to serve on the United States Supreme Court. In the U.S. presidential election of 1789, Harrison, a de facto member of the Federalist Party, received 6 electoral votes.
Harrison died in Charles County, Maryland. His parents were Richard Harrison, a member of the Maryland legislature, and Dorothy Hanson. He was married twice, and had two daughters, Sarah and Dorothy.