Jeff Bezos is having a super wedding–and likely has a super prenup, too. How the über rich do marriage contracts

Billionaire Amazon founder Jeff Bezos and former journalist Lauren Sánchez are having an extravagant multiday wedding in Venice this weekend that’s already attracted the media, celebrity guests—and more than a few protesters. The event is the culmination of a monthslong production by wedding planners and, very likely, by teams of lawyers who have combed through the couple’s complex finances to create an ironclad prenuptial agreement.

Both Bezos and Sánchez have been married and divorced previously...