Katie Holmes Gets an Indecent Proposal

A controversial, adulterous hookup website wants to "free Katie" from her husband! Mission Impossible ... Three!

TMZ has exclusively learned that AshleyMadison.com, an online dating service for married people, has offered the third Mrs. Cruise a free lifetime membership -- so she can seek out a "meaningful relationship" and "fill her lonely bed." Sometimes, a gal needs more than a battery-operated buddy! The site offers complete anonymity to all its members, and claims to have enrolled over 1.4 million wannabe cheaters -- including some of Hollywood's A-listers! Paging Charlie Sheen!

While Katie is used to getting offers she can't refuse, for once it isn't from her Scientolohubby! Deprogramming starts ... now!