"I Do! I Do!" is a 1966 Broadway musical based on the Jan de Hartog play "The Fourposter" with book and lyrics by Tom Jones and Score by Harvey Schmidt. The show originally starred Mary Martin (Original Broadway Maria in "The Sound of Music") and Robert Preston (Original Broadway Harold Hill in "The Music Man").

The musical opens on the morning of Agnes and Michaels wedding, and tracks their marraige over some fifty years. The set traditionally consists of their bedroom and the large fourposter bed which dominates the center of the room.

The original production opened on December 5, 1966 and ran for 560 performances.