Roswell Gilbert Horr (November 26, 1830 – December 19, 1896) was a politician from the U.S. state of Michigan.

Horr was born in Waitsfield, Vermont and moved with his parents to Lorain County, Ohio, in 1834, where he attended the public schools.

He graduated from Antioch College in Yellow Springs, Ohio, in 1857 and was clerk of the court of common pleas of Lorain County from 1857 to 1862 and reelected in 1860.

He studied law, was admitted to the bar in 1862, and commenced practice in Elyria, Ohio.

He was a delegate to the Republican National Convention in 1884 and was again an unsuccessful candidate for election in 1886 to the 50th U.S. Congress.