Sorry, Zac Efron. T.R. Knight is off the market.

The talented Grey's Anatomy actor recently went public with his new boyfriend, Mark Cornelsen, during the 2008 Elton John AIDS Foundation Oscar Party held at the Pacific Design Center in West Hollywood on Sunday night.

The two held hands and looked very happy together. See below:

Mark Cornelsen (left) and Grey's Anatomy's T.R. Knight.

T.R. Knight came out of the closet after infamously being outed during a fit of rage by former co-star Isaiah Washington, who ended up not being retained by Grey's Anatomy after the conclusion of its third season.

Knight received an Emmy nomination for Grey's Anatomy, while Washington went on to star in Bionic Woman, which got axed. Karma's a bitch.

Previously, Knight had been romantically linked to actor Luke MacFarlane, who went on to date Wentworth Miller of Prison Break fame.