I Do! I Do! is a musical with a book and lyrics by Tom Jones and music by Harvey Schmidt which is based on the Jan de Hartog play The Fourposter. The two-character story spans 50 years, from 1895 to 1945, as it focuses on the ups and downs experienced by Agnes and Michael throughout their marriage. The set consists solely of their bedroom, dominated by the large fourposter bed in the center of the room.

Thomas Collins Jones was an American lyricist and librettist, best known for The Fantasticks, 110 in the Shade, and I Do! I Do!.