Joshua Daniel Hartnett (born July 21, 1978) is an American actor. He began his career playing Michael Fitzgerald on ABC's Cracker (1997–1998), after which he became known as a teen idol through starring parts in films such as Halloween H20: 20 Years Later, The Faculty (both 1998), The Virgin Suicides (1999), Pearl Harbor, O, Black Hawk Down (all 2001), and 40 Days and 40 Nights (2002).
Hartnett continued to work steadily throughout the 2000s, with a mix of leading and supporting roles in Hollywood Homicide (2003), Wicker Park (2004), Mozart and the Whale, Sin City (both 2005), The Black Dahlia, Lucky Number Slevin (both 2006), Resurrecting the Champ, 30 Days of Night (both 2007), August (2008), and I Come with the Rain (2009). Subsequent credits include Bunraku (2010), Oh Lucy! (2017), Target Number One (2020), Wrath of Man (2021), Operation Fortune: Ruse de Guerre, and Oppenheimer (both 2023). For his portrayal of nuclear physicist Ernest Lawrence in the latter, Hartnett was awarded—alongside his co-stars—the Screen Actors Guild Award for Outstanding Performance by a Cast.
On television, Hartnett portrayed Ethan Chandler on the Showtime series Penny Dreadful (2014–2016), receiving nominations for three Fangoria Chainsaw Awards. He is married to actress Tamsin Egerton, with whom he has four children.
Source : Wikipedia
