Nathan Fillion (born March 27, 1971) is a Canadian actor known for his lead role as Captain Malcolm Reynolds in the television series Firefly and its film continuation, Serenity, his role as Joey Buchanan in One Life to Live and his current lead role as Richard Castle on Castle and as his role as Buck in Halo 3: ODST.

Fillion was born in Edmonton, Alberta, the son of Cookie and James "Culley" Fillion, both of whom are retired English teachers. He has an older brother, Jeff, and attended Holy Trinity Catholic High School, Concordia University College of Alberta and the University of Alberta, where he was a member of The Kappa Alpha Society. According to Fillion, he is descended from Confederate Lieutenant General Jubal A. Early.

After working in several theatre, television and film productions, including Theatresports with Rapid Fire Theatre and the improvised soap opera Die-Nasty, Fillion moved to New York City in 1994 where he acted in the soap opera One Life to Live as Joey Buchanan, for which he was nominated in 1996 for a Daytime Emmy Award in the "Outstanding Younger Actor" category. In 1997, he left the series to pursue other projects (but would return for a brief guest appearance in 2007). After moving to Los Angeles, he played a supporting role in the sitcom Two Guys, a Girl, and a Pizza Place and was cast as "James Fredrick Ryan" or "The Minnesota Ryan" in Steven Spielberg's Saving Private Ryan.