Scarlett Johansson is reportedly on the rebound from her split from Ryan Reynolds -- with Sean Penn!

Scarlett Johansson and Sean Penn
The two have been having a "fling" since January, when ScarJo was staying at the Chateau Marmont in L.A. while filming "We Bought a Zoo," according to Us Weekly.

A source tells the magazine, "Scarlett's smitten with him."

Johansson, 26, and Penn, 50, have a shared interest in relief for Haiti. Scarlett reportedly "first reached out to Sean when she was planning to visit Haiti," where Sean was living.

Both Scarlett and Penn recently went through high profile break-ups. Johansson and Ryan Reynolds filed for divorce in December and Sean Penn and Robin Wright Penn finalized their divorce last July.