X-Factor Investigations is a fictional detective agency created by writer Peter David for the Marvel Comics comic book series X-Factor (vol. 3). The agency first appears under the name XXX Investigations in the first issue of the Marvel Comics limited series Madrox #1 (November 2004). In the final issue, Madrox #5 (March 2005), the name is changed to X-Factor Investigations, and later abbreviated XF Investigations.