Chaos Theory is a 2008 American comedy drama film starring Ryan Reynolds, Emily Mortimer, and Stuart Townsend. The film was directed by Marcos Siega, written by Daniel Taplitz and Kathy Gori, and was shot in Coquitlam and Squamish, British Columbia.

Obsessively organized efficiency expert Frank Allen tells his future son-in-law Ed how his life had unraveled in unexpected ways when he was forced to learn to forgive his wife's transgression, in response to his cold feet.

The film performed poorly in theaters and was not positively reviewed by critics.