Cecily Legler Strong (born February 8, 1984) is an American actress and comedian who was a cast member of Saturday Night Live from 2012 to 2022. She was born in Springfield, Illinois, and raised in Oak Park, Illinois, an inner-ring suburb of Chicago. She is the daughter of Penelope and William "Bill" Strong, who worked as an Associated Press bureau chief and is now managing partner at a Chicago public relations firm. Strong's parents are divorced. Strong grew up adoring SNL as a child, reenacting sketches with her friend and watching old SNL commercials on VHS. "I had a tape of the best commercials, and I wore it out every day." She has stated that Phil Hartman inspired her.

She attended Oak Park and River Forest High School before transferring for her senior year to the Chicago Academy for the Arts, where she graduated in 2002. She then studied acting at California Institute of the Arts (CalArts), graduating in 2006 with a BFA in theatre. After graduating from CalArts, Strong returned to Chicago, where she studied at the Second City Conservatory and iO Chicago.