John R. Williams (May 4, 1782 – October 20, 1854[1]) was an American soldier, merchant, and politician who is best known for serving as the first mayor of Detroit, Michigan, after the city's reincorporation.

[3][4] His father, who had been active in civic and political affairs,[1] died before December 12, 1785, at which time Joseph Campeau (which he generally spelled Campau) leased a house to Cecile (widow of Thomas Williams) that was located north of the Detroit River and adjacent to Joseph Campau's property.

[1][2] One of them, Union General Thomas Williams, was killed in action during the Civil War at the Battle of Baton Rouge in 1862.

[1] Upon leaving the army, he returned to Detroit and joined his uncle, Joseph Campau, in his successful mercantile business.

[1] After the end of the war, Williams was appointed Associate Justice of the County Court for Michigan in 1815.

[1] Besides serving as mayor, Williams was a landowner, merchant, and bank president during his lifetime.