The couple tied the knot over the weekend in Los Angeles, Us Weekly reported.
"Nuptials," Mara captioned a photo on Instagram that features herself kissing Bell during their wedding reception.
Bell shared the same photo on Twitter, writing, "Me & Mrs. B."
Mara, 34, and Bell 31, became engaged in January after they started dating in the fall of 2015. This is the second marriage for Bell, who was previously wed to Westworld star Evan Rachel Wood. Bell and Wood share a 3-year-old son together.
Bell and Mara starred together in 2015's Fantastic Four. "We fell in love on the press tour," the actress said while appearing on Watch What Happens Live with Andy Cohen in May of when her romance with Bell began.