KANYE WEST First Appearance in a Year PERFORMS WITH KID CUDI | WATCH VIDEO

Kanye West surprised the crowd at Kid Cudi's concert Saturday night with his first appearance on stage in a year.

Kanye and Cudi performed "Father Stretch my Hands, Pt. 1" at Chicago's Aragon Ballroom.  Cudi's in the middle of his Passion, Pain & Demon Slayin' World Tour.

Kanye hasn't been on stage since cancelling his Saint Pablo Tour last November.  You'll recall he had a mental breakdown and ended up at the UCLA psychiatric ward, but he has bounced back in a big way.

-TMZ