Ion Storm, L.P. was an American video game developer founded by video game industry veterans John Romero and Tom Hall, both formerly of id Software. Despite an impressive pedigree and high expectations, the company only produced one commercial and critical success, 2000's Deus Ex.

The company was founded in Dallas, Texas in November 1996; a branch in Austin, Texas was opened in 1997. In April 1999, Eidos Interactive acquired 51% of the studio in exchange for advances to the developers. The Dallas studio closed in July 2001, leaving the Austin office as the new headquarters; after financial struggles at Eidos Interactive, the Austin studio followed with its own closure in February 2005.