Paris Hilton, on a romantic Valentine's day vacay with her boyfriend Doug in Rio, donned a Brazilian bikini that showed off her backside on the balcony of her hotel, the Copacabana Palace.

When in Rio...

Who says having a wedding is everything? Sure, some of these cute couples might be engaged - or are ABOUT to be engaged - but Valentine's Day is about love, not marriage...

Madonna and Jesus? A holy union! Miley and Liam? Young love is the sweetest! Then there's Paris and Doug and Kim and Reggie. Hey, maybe they'll all have engagement rings on their fingers by tomorrow morning!

As for Katy and Russell, we look forward to their upcoming nuptials. But in the meantime, today is about love and romance, flowers and chocolates... and seeing Valentine's Day, natch!

They're def back on! The hottest May-December romance of all.

Check out Material Girl Madonna and her boy toy Jesus Luz leaving a club in Rio last night with big smiles on their faces. Actually, M is the only one actually smiling. I dunno if I'd be happy being Jesus - you'd think he'd want a younger woman!

Either way, happy V-day to both!

So what if you're single? This is LA! Just go out clubbing with friends and everything will be fine! That's what Kristin Cavallari did last night at Voyeur - nothing like celebrating Valentine's Day with drinks and dancing!

All those of years of partying are forever etched on her face...

Blonde bombshell Pamela Anderson put on a slinky dress Saturday night and dined out at Katsuya in Hollywood. 42-years-old, huh? Pam still has the bod, but the face is a different story. Picture perfect?

Such pretty smiles! I know V is my fave, but Seraphina looks so adorbs in these pix, right? Cuteness. Supermom Jen Garner took her daughters and co. to Toscana in Brentwood on Saturday.

I just saw Jen in Valentine's Day and she was absolutely lovely in it. For her sake, PLEASE let Ben Affleck pencil in some face time with her today... please? She deserves it!

Katy Perry might not be the most gifted musician, but she does always look fab! The pop princess - engaged to Brit funnyman Russell Brand - stopped by Wax on Melrose on Saturday...

Ooh la la! Guess she's got an extra special surprise planned for her soon-to-be-hubby today!

Poor thing! When's Rob when you need him? Twilight's Kristen Stewart was spotted driving alone in her Mini Cooper over Valentine's Day weekend. Thankfully she has a couple of fat paychecks to comfort her!