Big Bang Theory
Big Bang Theory most commonly refers to:

The Big Bang, a cosmological model of the universe
The Big Bang Theory, an American TV sitcomIt may also refer to:

Music
Big Bang Theory (song), Barenaked Ladies (2007) themesong to the U.S. TV sitcom, see The Big Bang Theory#Theme song
Big Bang Theory (Billy Bang album) (2000)
Big Bang Theory (Styx album) (2005)
Big Bang Theory (Harem Scarem album) (1998)

Other uses
"The Big Bang Theory" (Family Guy), a 2011 episode of the TV series

See also
Big Bang (disambiguation)