UFC 94: St-Pierre vs. Penn 2 was a mixed martial arts (MMA) pay-per-view event promoted by the Ultimate Fighting Championship (UFC) on January 31, 2009. The card featured five televised MMA bouts, as well as five un-aired preliminary bouts. It was the second UFC event of 2009 and took place on the weekend of Super Bowl XLIII.

The main event featured the UFC Welterweight Champion, Georges St-Pierre, successfully defending his title with a 4th round technical knockout (TKO) over UFC Lightweight Champion B.J. Penn. This represented the first time two current titleholders competed against each other in the UFC. Penn also sought to become the first fighter in the UFC to concurrently hold two championships in two separate weight classes. The contest was heavily promoted, featuring a publicity tour to Canada and Hawaii, as well as the introduction of UFC Primetime, a preview show that cost $1.7 million to produce. The co-main event of the evening was a battle between two undefeated light heavyweights sporting 13–0 records in Lyoto Machida and Thiago Silva. Machida was victorious via 1st round knockout and became the next challenger for the UFC Light Heavyweight Championship.

The contest between St-Pierre and Penn was a source of significant controversy. During the fight, members of the Nevada Athletic Commission (NSAC) noticed Phil Nurse, one of St-Pierre's cornermen, applying petroleum jelly (brand name Vaseline) to his fighter's back, which is illegal under NSAC rules. This event triggered formal complaints filed by Penn and formal defenses from St-Pierre's camp. The controversy culminated in a hearing at the NSAC, and following its conclusion, NSAC Executive Director Keith Kizer stated that there would be no penalties levied against St-Pierre or his camp. However, the committee left it ambiguous whether the matter was conclusively closed.