William Rufus Terrill (April 21, 1834 – October 8, 1862) was a United States Army soldier and general who was killed in action at the Battle of Perryville during the American Civil War.

The encounter caused a one-year suspension for Sheridan from the academy, though the two renewed their acquaintance while serving under Don Carlos Buell in the Civil War.

Terrill, however, left no doubt about where his loyalties lay, telegraphing the War Department and General Winfield Scott from Poughkeepsie, New York, on April 29, 1861, that "I am now and ever will be true to my oath and my country.

The elder Terrill wrote his son a scathing letter of disapproval saying "Can you be so recreant and unnatural as to aid in the mad attempt to impose tyranny upon your kith and kin?

William Terrill served as assistant inspector general in Washington, D.C., and then commanded a battery of artillery in the Army of the Ohio at the Battle of Shiloh.

Around 4:00 PM, a Confederate artillery shell exploded near Terrill, driving a piece of shrapnel into his upper chest and ripping through his left lung.

The previous night, Generals Terrill and James S. Jackson and Colonel George Webster were discussing the improbability of being killed in action.

In 1864, during the Overland Campaign, Terrill's brother James, by then commanding a brigade, was killed in action at the Battle of Bethesda Church and buried on the battlefield.