Meagan Good & Joseph Gordon-Levitt
The duo reportedly started dating after meeting on the set of the 2005 film Brick, but they only stayed together for six months.
Joshua Jackson & Rosario Dawson
The Dawson's Creek alum and the Josie and the Pussycats star dated for about a year back in 2002.
Chris O'Donnell & Reese Witherspoon
The NCIS: LA stud and America's sweetheart dated way back in 1993, when 17-year-old Witherspoon first moved to Los Angeles.
Sarah Jessica Parker & Robert Downey Jr.
The man who now rocks the Iron Man suit for Marvel admitted that drugs and alcohol were to blame for the end of his seven-year relationship with the Sex and the City star. "I liked to drink, and I had a drug problem, and that didn't jibe with Sarah Jessica," he admitted in an a 2008 interview with Parade, "because it is the furthest thing from what she is. She tried to help me. She was so miffed when I didn't get my act together."
Matthew Perry & Heather Graham
The late Friends alum and The Hangover star supposedly had a fling 2003, but it didn't last long enough to be more than a little blip on the Hollywood hookup radar.
Tom Hiddleston & Kat Dennings
The 2 Broke Girls actress dated her Thor costar briefly in 2010, appearing very cozy while attending Comic-Con to promote the Marvel film. But their relationship fizzled by the time the movie premiered the following year.
Ryan Reynolds & Kristen Johnston
In 1999, way before he wed Blake Lively, Reynolds dated the 3rd Rock From the Sun star. The duo even attended the premiere of The Green Mile together.
Jake Gyllenhaal & Natalie Portman
The child actors turned A-listers briefly dated in 2006 but remained close friends—and co-starred in the intense 2009 drama Brothers.
"She's a vegan," Gyllenhaal pointed out when presenting Portman with the Desert Palm Achievement Award in 2011, "which makes it really frustrating when you're picking a place to eat."
Ted Danson & Whoopi Goldberg
This relationship was laced with scandal, as the Cheers actor's affair with his Made in America costar back in 1992 led to his divorce from producer Casey Coates.
Cameron Diaz & Matt Dillon
Diaz and Dillon began dating in 1995, but broke up shortly after they wrapped filming on the 1998 comedy There's Something About Mary.
Julie Bowen & David Spade
Spade's dating roster reads like a who's who of hot Hollywood blondes: Heather Locklear, Nicollette Sheridan and Playboy Playmate Jillian Grace. In 2002, he added the Modern Family star to that list, but the couple called it quits after a year of dating.
Ashton Kutcher & January Jones
Before marrying Mila Kunis, Kutcher dated Jones from 1998 to 2001. And according to the Mad Men star, he was not a very good boyfriend at the time. "He was not supportive of my acting," Jones told GQ in 2009. "He was like, 'I don't think you're going to be good at this.' So, f--k you!"
Michael Keaton & Courteney Cox
The one where the Friends alum dated Batman. The couple broke up in 1995 after more than six years together, with Cox telling People shortly after the split, "It's the most important relationship I've ever had, and I think he's the most wonderful person I've ever met."
Winona Ryder & Jimmy Fallon
The SNL alum was linked to Ryder in 2002, but she denied a hookup to W magazine, insisting that the two were "just friends."
Helen Hunt & Matthew Broderick
Before he met wife Sarah Jessica Parker, the Broadway vet was smitten with Hunt in 1987. The two remained friends after the split, even starring in 2008's Then She Found Me together.
David Gallagher & Megan Fox
Before she married and had three children with ex-husband Brian Austin Green, Fox dated the 7th Heaven star from 2003 to 2004.
Alyssa Milano & Justin Timberlake
The Charmed actress and the singer dated briefly after he and Britney Spears broke up in 2002.
Chris Pratt & Emily VanCamp
Before she went on a Revenge spree and he became a Marvel superhero, Pratt and VanCamp met and fell in love while playing brother and sister on the WB's Everwood. They broke up in 2007.
Josh Groban & January Jones
The singer calls his two-and-a-half year early aughts courtship with Jones his longest relationship ever. "We were madly in love. It was definitely my longest relationship," he told Details in 2013. "I'd love to get into another serious relationship. I am a real romantic at heart."