Joseph Cabell Breckinridge Sr. (January 14, 1842 – August 18, 1920) was a Union Army officer from Kentucky during the American Civil War.

His father served as a leader of the Kentucky emancipation party in 1849 and was a strong Union man in 1861 at the outbreak of the Civil War.

[2] In August 1861, Breckinridge joined the U.S. Army and was appointed an aide-de-camp to George H. Thomas, and served with him at Mill Springs and Shiloh.

After being exchanged, he served out the remainder of the war as a mustering officer, and received brevet promotions to captain (July 1864) and major (March 1865).

He served on the staff of V Corps in Cuba and was engaged in the battles of El Caney and San Juan Hill, where he had a horse shot from under him.