Leonard Leakey Hofstadter, Ph.D., is a fictional character portrayed by Johnny Galecki in the CBS sitcom, The Big Bang Theory. Leonard is an experimental physicist who shares an apartment with colleague and best friend, Dr. Sheldon Cooper. For his portrayal, Galecki was nominated for a Primetime Emmy Award and a Golden Globe Award in 2011.

John Mark Galecki is an American actor. He played Leonard Hofstadter in the CBS sitcom The Big Bang Theory (2007–2019) for which he received a Primetime Emmy Award nomination, and David Healy in the ABC sitcoms Roseanne and The Conners (2018–2019). Galecki also appeared in the films Prancer (1989), National Lampoon's Christmas Vacation (1989), Suicide Kings (1997), I Know What You Did Last Summer (1997), Bookies (2003), In Time (2011), and Rings (2017).