John Christopher Reilly is an American actor. He is known as a character actor taking leading and supporting roles in independent drama films and studio comedies. He gained exposure through his supporting roles in Paul Thomas Anderson's films Hard Eight (1996), Boogie Nights (1997) and Magnolia (1999), and Martin Scorsese's Gangs of New York (2002) and The Aviator (2004). Reilly was nominated for the Academy Award for Best Supporting Actor and the corresponding Golden Globe Award for his role in the musical film Chicago (2002). Reilly's other notable films include The River Wild (1994), The Thin Red Line (1998), and The Hours (2002).

Boogie Nights is a 1997 American period drama film written, directed, and co-produced by Paul Thomas Anderson. It is set in Los Angeles's San Fernando Valley and focuses on a young nightclub dishwasher who becomes a popular star of pornographic films, chronicling his rise in the Golden Age of Porn of the 1970s through his fall during the excesses of the 1980s. The film is an expansion of Anderson's mockumentary short film The Dirk Diggler Story (1988), and stars Mark Wahlberg, Julianne Moore, Burt Reynolds, Don Cheadle, John C. Reilly, William H. Macy, Philip Seymour Hoffman, and Heather Graham.