"I Won't Last a Day Without You" is a song with lyrics written by Paul Williams and music composed by Roger Nichols. It became a hit single for the Carpenters in 1974, reaching number eleven on the Billboard Hot 100 chart and number one on the easy listening chart. It was the Carpenters' ninth number one on the easy listening chart.

In 1972, Richard Carpenter had learned of a new song from Williams and Nichols, who had already contributed "We've Only Just Begun" and "Rainy Days and Mondays" to the Carpenters. He included it on their 1972 album A Song for You, but it would not be released as a single until 1974. Before then, Diana Ross heard it and included it on her 1973 album Touch Me in the Morning, as well as the B side of the title track single release, which became a number-one hit. Williams released his version as a single in 1973, but garnered only minor success. Maureen McGovern recorded the song and also released it as a single in 1973 (and included on her album The Morning After), but it also failed to become a hit. The Carpenters' version was released as a single the following year.

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