Which character is known as 'McSteamy'?

Mark Sloan is the Grey's Anatomy character known as "McSteamy." Played by Eric Dane, he is a highly skilled plastic surgeon whose looks and romantic reputation inspire the nickname.

Mark first appears in the second-season episode "Yesterday" as Derek Shepherd's former best friend. Their friendship was damaged after Mark had an affair with Derek's wife, Addison Montgomery. He later moves to Seattle and joins the staff at Seattle Grace as the hospital's plastic-surgery specialist.

The nickname is part of the show's playful "Mc" tradition. Meredith and the other interns are associated with Derek Shepherd's nickname, "McDreamy," while Mark becomes "McSteamy." The name reflects his image as confident, flirtatious, and famously attractive, but Mark's story eventually develops beyond that persona.

He becomes especially important through his relationships with Lexie Grey and Callie Torres, his mentorship of Jackson Avery, and his friendship with Derek. After Mark's death following the season-eight plane crash, Seattle Grace Mercy West is renamed Grey Sloan Memorial Hospital in tribute to him and Lexie.