Calvin Harris -- My Fair DJ (PHOTO)

Calvin Harris wasn't always the hot guy slaying the hottest girls ... it wasn't that long ago he was geeky, awkward, unkempt and in need of a shower.

Harris was photographed in Australia in 2008 ... way before he hit it big, buffed up big-time, and started dating the likes of Rita Ora and Taylor Swift.

Since then, he's cut and colored his hair, hit the gym, fixed his teeth and discovered the sun.

Oh yeah, and made millions and millions and millions of dollars.

Props to the Daily Mail for unearthing the epic pic.