William "Buck" McCandless (September 29, 1834 – June 17, 1884) was an American military officer and politician from Pennsylvania.

He served in the Union Army during the American Civil War and commanded a regiment and then a brigade in the Pennsylvania Reserve Division.

[1] McCandless enlisted in the 2nd Pennsylvania Reserve Regiment, as a private; but he was promoted to the rank of major in June 1861.

)[2] When William Sinclair was wounded in the Battle of Fredericksburg, McCandless succeeded him in command of the 1st Brigade of the Reserves under George Gordon Meade.

After Fredericksburg, the division was transferred to the defenses of Washington, D.C., to recuperate from its losses on active duty.

On the second day of the battle, McCandless moved to the army’s left and deployed his men in two lines, together with the 93rd Pennsylvania Infantry of Frank Wheaton’s brigade, at the foot of Little Round Top.

McCandless’ brigade, under immediate supervision by Crawford, launched a counterattack against the Confederates, mostly from William T. Wofford’s command, across Plum Run Valley and up slope to the edge of the Wheatfield on July 2, 1863.