John William Killilay (May 24, 1887 – October 21, 1968) was a pitcher in Major League Baseball who played for the Boston Red Sox during the 1911 season. Listed at 5 ft 11 in (1.80 m), 165 lb., Killilay batted and threw right-handed. He was born in Leavenworth, Kansas.
Killilay posted a 4-2 with 28 strikeouts and a 3.54 ERA in 14 appearances, including seven starts, one complete game, and 61 innings of work.
Killilay died in Tulsa, Oklahoma at age 81.