Jason Iain Flemyng is an English actor. He is known for his work with British filmmakers Guy Ritchie and Matthew Vaughn appearing in the Ritchie films Lock, Stock and Two Smoking Barrels (1998) and Snatch (2000), and appearing in Vaughn's films Layer Cake (2004), Kick-Ass (2010), and X-Men: First Class (2011).

The League of Extraordinary Gentlemen, also promoted as LXG, is a 2003 steampunk/dieselpunk superhero film loosely based on the first volume of the comic book series of the same name by Alan Moore and Kevin O'Neill. Distributed by 20th Century Fox, it was released on 11 July 2003 in the United States, and 17 October in the United Kingdom. It was directed by Stephen Norrington and starred Sean Connery, Naseeruddin Shah, Peta Wilson, Tony Curran, Stuart Townsend, Shane West, Jason Flemyng, and Richard Roxburgh. It was Connery's final role in a theatrically released live-action film before his retirement in 2006 and death in 2020.