William Thomas Harbaugh Brooks (January 28, 1821 – July 19, 1870) was a career military officer in the United States Army, serving as a major general during the American Civil War.

He was promoted to captain, 3rd U.S. Infantry, on November 10, 1851, then served on frontier duty in the New Mexico Territory until 1858, at times skirmishing with local Navajos.

Recovering, he resumed command of his brigade for the Maryland Campaign and led his men at Crampton's Gap, where they captured a Confederate battle flag belonging to the 16th Virginia Infantry.

At the Battle of Antietam, Brooks's brigade was mainly in reserve, although under "galling fire of both artillery and sharpshooters" for 48 hours.

This demotion has been blamed on Brooks's being involved in intrigues by VI Corps commanders against Maj. Gen. Ambrose Burnside after Fredericksburg.

Returning to field duty in the late spring of 1864, Brooks commanded the 1st Division of XVIII Corps at Cold Harbor and Petersburg.

Most of Early's combat strength was deployed to the south of town, where Federal troops had achieved their most significant successes during the December battle.

[3] At first Sedgwick believed that he faced a single brigade of infantry, so about 3:30 p.m. he attacked the Confederate positions with only William T. H. Brooks division.