It's Heidi Klum's birthday and we're celebrating by taking a look at her hottest snaps from over the years ... and with 53 trips around the sun, there's a lot to soak in.

Say this for Heidi ... this German-American model spends a whole lotta time in a bikini. When Heidi isn't showing off her fantastic bod, you can catch her doing the millions of other projects that keep her busy ... all while looking like a complete dime.

Heidi's way more than a pretty face ... she's a businesswoman, actress and even a painter!!!

In other words, this busy woman deserves the relaxation and sunbathing she does year-round.

Check out the gallery ... and happy birthday, Heidi, never stop blessing us with your posts!!!