The 74-year-old actor looks quite dapper in the photo, and sports a green scarf, purple sweater and a huge smile. McKellen writes that the picture was taken backstage at the Grand Theatre in Leeds in 1970.
The actor recently finished a Broadway production of Samuel Beckett's Waiting for Godot with best friend and fellow actor Patrick Stewart. The two appear as Magneto and Professor X, respectively, in X-Men: Days of Future Past. The movie debuts in theaters May 23.
McKellen will also reprise his role as the wizard Gandalf in the third and final Hobbit film, The Battle of the Five Armies, on December 17.