"When I Said I Do" is a song written by American country music singer Clint Black, and recorded by Black and his wife Lisa Hartman Black as a duet. It was released in August 1999 as the first single from Black's album D'lectrified. The song reached the top of the U.S. Billboard Hot Country Singles & Tracks chart and the Canadian RPM Country Tracks chart. It also peaked at number 31 on the U.S. Billboard Hot 100, making it a crossover hit. It is one of only two chart singles for Lisa Hartman Black. The song was later covered by then-husband and wife Kenny Lattimore and Chanté Moore on their album Things That Lovers Do.

This song discusses the narrators' vow to stay together until the end of their lives.

The music video was directed by Clint Black himself and premiered in September 1999.

"When I Said I Do" debuted at number 45 on the U.S. Billboard Hot Country Singles & Tracks chart for the week of September 4, 1999. For the chart dated December 4, 1999, it became Clint's thirteenth and final number one single on that chart, and the only number one single for Lisa. The following week, it fell to number two, being replaced at the top by Brad Paisley's "He Didn't Have to Be". It then returned to number one on the chart dated December 18 for a second and final week, making for two nonconsecutive weeks at the top.