It's Mother's Day, and if there's one thing we know about Hollywood ... it's that they love their mamas, and aren't afraid to show it. 

Tons of stars posted photos Sunday shouting out their moms, themselves, and/or their baby mamas. Some of the A-listers who heart Mom include Ryan Seacrest, Tom Brady, Jessica Alba, Drake, Drew Barrymore, Oprah, Justin Bieber, Nicki Minaj ... and lots more.

Remember ... if it weren't for all of these special ladies, none of our favorites celebs would even exist! So give it up for the mama bears of the world today -- they've earned it.