"So Happy" is a single by Theory of a Deadman, and the first to be released from their third album Scars & Souvenirs. It was officially released to radio on February 11, 2008, although many rock stations in the United States added it to their rotations earlier. "So Happy" debuted on Billboard's Mainstream Rock Tracks chart on February 9, 2008, and peaked at #2 on April 5, 2008. The song needed only three weeks to become a top-10 hit on the Mainstream Rock chart, making it their fastest top-10 entry to date. It is also the band's first top-20 hit on the Modern Rock Tracks chart. In Canada, it debuted (and peaked) at #58 on the Canadian Hot 100 on March 8, 2008.

The song features Shinedown vocalist Brent Smith performing backing vocals.

The music video first aired on MuchMusic in the middle of April 2008. It peaked on the MuchMusic Countdown at #10.

The video features Serinda Swan and was directed by Colin Minihan.

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