William Guarnere, American sergeant (d. 2014)
William J. Guarnere Sr. (April 28, 1923 – March 8, 2014) was a United States Army paratrooper who fought in World War II as a non-commissioned officer with Easy Company, 2nd Battalion, 506th Parachute Infantry Regiment, in the 101st Airborne Division.

Guarnere wrote Brothers in Battle, Best of Friends: Two WWII Paratroopers from the Original Band of Brothers Tell Their Story with long-time friend Edward "Babe" Heffron and journalist Robyn Post in 2007. Guarnere was portrayed in the 2001 HBO miniseries Band of Brothers by Frank John Hughes.