It's Sophia Bush!
"Hey #Russia. I kissed a girl. And I liked it," said Sophia, who played Brooke Davis on One Tree Hill, to Instagram, adding the hashtags. "#boycottRussia #LGBTQequality #BoycottSochi."
Sofia's referencing the 2014 Winter Olympics, scheduled to take place in Sochi, Russia; recently passed laws in the region prohibit, in vaguely-worded terms, some (or all) public displays of homosexuality or support toward homosexuality. Read more about the gay rights situation in Russia here.
Sophia's partner-in-kissing is 21-year-old Australian musician Betty Who.
Did you guess who she was? Click here to play more Guess Who!