Sean Penn, Scarlett Johansson and More Summer Celebrity Splits

June 7, 2011— -- The summer fling: It's a rite of passage for many people and celebrities are no exception. (Jennifer Aniston has gotten the season sizzling early with her newly revealed beau, Justin Theroux.)

As the mercury rises and the days get longer, some stars are dumping the warm body that got them through the winter months in favor of a new model. Hollywood's latest reported split: Sean Penn and Scarlett Johansson, the unlikely couple who were all over each other until just recently.

Below, check out what happened with Penn and Johansson and find out who else has split in time for summer.

Sean Penn and Scarlett Johansson

Popular opinion sided with Hollywood darling Johansson, 26, when she filed for divorce from hunky husband Ryan Reynolds in late 2010, but many star-watchers switched teams when reports circulated that she had begun dating 50-year-old Penn in March. They were seen cozying up to one another all over L.A., were photographed sharing a steamy 24-hour vacation getaway to Mexico, and were spotted smooching at the White House Correspondents' Dinner.

Was it was all too much too soon? People magazine reported last week that the couple split, but at Spike TV's Guys Choice Awards in Los Angeles, Calif., last weekend, they looked like the picture of bliss in a photo taken backstage. Maybe this spring fling will heat back up again in the coming months.

Ryan Phillippe and Amanda Seyfried

It's a classic recipe for disaster: Date famous blonde. Find out ex-girlfriend is pregnant while dating said famous blonde. Let chaos ensue.

People magazine reported that the "Cruel Intentions" star and "Mean Girls" actress met at Kate Hudson's annual Halloween party last year and since then have shared a low-key, casual romance. Even so, Ericka Souter, staff writer at Us Weekly magazine, told ABC News that "everyone was surprised when Amanda stuck by him when rumors were flying that Alexis Knapp was pregnant with Ryan's baby," and "although the attraction was mutual with this low-key couple, it was a mutual split when the relationship ran its course."

Adrienne Curry and Christopher Knight

Reality-TV fans everywhere were rooting for this famously eccentric couple. Curry, a former "America's Next Top Model" contestant and Knight, who played Peter Brady in "The Brady Bunch," first met as housemates on the VH1 series "The Surreal Life" and had been married for five years before recently splitting.

Souter revealed that the split seems to have hit Knight particularly hard, saying, "He looks pained by the decision in his photographs out, it seems like the differences that brought them together ultimately tore them apart." Curry's Twitter activity indicates she's also upset about the breakup. Last week, she wrote, "I am separated from my husband" and talked about a 10-pound weight loss because of stress.

Emily Maynard and Brad Womack

What can go wrong when you start a relationship with hot air balloon rides, champagne-fueled picnics and fabulous vacations on a hit reality-TV show? Sometimes, a lot. "Bachelor" Womack proposed to Maynard on a South African vineyard with a spectacular diamond. What came to follow was the harsh reality that they live in separate cities; she in her native Charlotte, N.C., he in Austin, Texas. As US Weekly reported, they had "serious issues to work out."

Lady Gaga and Luc Carl

A few weeks ago, during an appearance on England's popular "The Graham Norton Show," pop sensation Lady Gaga announced that she's single, saying, "I don't have a boyfriend and I haven't been on any dates recently." (Ironically, she chose to wear a wedding dress to make her statement.)

Her split from Luc Carl, a New York City based bartender and musician whom Gaga had been dating for on and off for a few years, seems to have been a painful one for the two of them. Lady Gaga had famously cited Carl as an inspiration for her music, but with her success came frequent travel and work, which might have put a strain on her relationship.

Hayden Panettiere and Wladimir Klitschko

These two shared a 15-inch height difference, but the vertical challenge didn't stop them from dating. But the lateral distance between them ended their relationship, as heavyweight boxing champ Klitschko told People magazine. "We had a great time together, but it's not that easy to manage a relationship between two continents," he said.

Actress Panettiere told People, "Even though we've decided splitting up is best for both of us, we have an amazing amount of love and respect for each other and remain very close friends."

Leonardo DiCaprio and Bar Rafaeli

The Hollywood heavyweight and world-class model made a gorgeous duo but, alas, it was not meant to be. Rafaeli, 25, doesn't appear too upset about her recent split from DiCaprio, as she was photographed frolicking on yachts at the Cannes Film Festival during the day and partying on the town at night.

DiCaprio doesn't seem to be losing sleep over the breakup either. He has been spotted in Italy with "Gossip Girl" star Blake Lively.

Joe Jonas and Ashley Greene

Tons of tweens celebrated Jonas and Green. Pictured as the perennially sweet boyfriend, the "Jonas Brothers" crooner seemed to be the perfect guy for "Twilight" star Greene, until their relationship ended. They reportedly broke up close to Greene's 24th birthday. But the starlet has been seen out and about on the beaches and red carpets of L.A. while Jonas seems to be coping just fine by bonding with his bulldog, Winston.

Bradley Cooper and Renee Zellweger

These two box office darlings dated less than two years, but from the first time they were linked together, their relationship was more of an undercover romance than front-page tabloid fodder. Rumors flew that Zellweger, 42, had back burnered her career to be a good girlfriend to Cooper, 36, who embraced leading-man status earlier this year with "Limitless."

By all accounts, however, their romance seems to have simply petered out, with Cooper enjoying a lifestyle that conflicted with the low profile that Zellweger preferred. He seems to have moved on to a flashier star: Olivia Wilde of "House" and the film "Tron: Legacy."