The couple married in September 2008 but are now said to be living along. The split was evidently amicable, and while the couple has been separated for two weeks, it's unclear whether either actor has immediate plans to file for divorce.
Both Johansson and Reynolds have been super-busy with work (especially the latter), and apparently it was the time apart that made Johansson unhappy, according to Us Weekly.
Reynolds next stars as Hal Jordan in WB's "Green Lantern," while Johansson has her own superhero franchise to compete with, as the "Iron Man 2" actress will reprise the role of Black Widow in Joss Whedon's "The Avengers."
She's also about to play Matt Damon's wife in Cameron Crowe's "We Bought a Zoo," while Reynolds has been busy filming the Universal comedy "The Change-Up" with Jason Bateman and "Tron: Legacy" star Olivia Wilde.
Reynolds was recently named People magazine's Sexiest Man Alive, and Johansson has won her share of similar awards.