Drew Brees is showing off his brand new look -- a buzz cut -- and it's for a great reason!!

The New Orleans Saints QB took some clippers to the dome on Tuesday for the Saving By Shaving charity event for the Boston Children's Hospital ... and helped raise a TON of money.

For a guy who's pretty calm under pressure, Brees looked a bit nervous to try out the new 'do (or lack, thereof) ... but cracked a few jokes in the process!!

"It's gonna be a lot easier to wash my hair now!!," the 41-year-old said.

The best part?? Brees says Granite CEO Rob Hale made an incredible $7 MILLION donation during the event.