Hollywood's Stars Celebrate Mother's Day

It's Mother's Day, and if one group of people that know how to give it up for their Mama Bears -- it's Hollywood's rich and famous ... which they certainly did this year.

The biggest stars made sure to heap on tons of love/praise for their moms Sunday, with tribute posts going up left and right on social media. Some are mothers themselves, others were shouting out their baby mamas ... but almost everyone was expressing gratitude.

Some notable posts ... Kim Zolciak, who's going through a divorce, posed with 2 of her kids; Usher snapped something with his mom; Justin Timberlake gave Jessica Biel her flowers; Travis Barker lauded Kourtney Kardashian; and Alec Baldwin shared his own mom memories.

There were other sweet snaps as well ... shared by the likes of Simu Liu, Patrick Mahomes, Rebel Wilson, Priyanka Chopra, Kylie Jenner, J Lo, Bethenny Frankel and others.

BTW, while there are certainly a lot of moms who give birth to celebs ... there are probably just as many who are famous themselves. As it goes, the apple doesn't fall far from the tree.

Some of our fave notable mommies ... Teresa Giudice, Serena Williams, Kim K, Meghan Markle, Chrissy Teigen, Heidi Klum, Cardi B, Eva Longoria, Kris Jenner, Gabrielle Union, Kate Hudson, Beyonce, Reese Witherspoon, Angela White, Lisa Bonet ... just to name a few.