Justin Chambers turns 41 today. Give it up for the actor and father of five!

A regular on Grey's Anatomy from day one, but a much bigger part of the show of late, Justin has really come into his own in recent seasons as Dr. Alex Karev.

He's played the complex, macho doc so well from the start and remains a terrific part of one of TV's best ensemble casts. Keep up the good work, Justin!

In honor of the occasion, here are some photos of the star, on and off set:

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.