"Can't Let Go" is a ballad written and produced by American singer and songwriter Mariah Carey and Walter Afanasieff, and recorded for Carey's second album Emotions (1991). It was released as the album's second single in the fourth quarter of 1991 in the United States and the first quarter of 1992 elsewhere. The protagonist of this synthesizer-heavy ballad laments an ex-lover who has moved on, and though she tries she "can't let go."

Carey had fallen out with her songwriting partner Ben Margulies following a financial dispute, and her record label suggested that she work with the other producers of her debut album such as Rhett Lawrence, Ric Wake and Narada Michael Walden. She chose Walter Afanasieff, who had produced her second single "Love Takes Time" (1990), and "Can't Let Go" was one of the songs they created. After the release of the single "Emotions," "Can't Let Go" was promoted on both The Arsenio Hall Show in September 1991 and Saturday Night Live in November 1991 when she was the musical guest in the episode which featured Linda Hamilton as the host. "Can't Let Go" was later included on Carey's The Ballads (2008).

"Can't Let Go" is written in the key of F major. The song is based heavily upon Keith Sweat's "Make It Last Forever". Mariah's vocals here range from the low note of F₃ to the high note of C♯₇, at a moderately slow tempo of 81 beats per minute, according to Musicnotes.com.

Allmusic editor Ashley S. Battel wrote that "yearning cries for a lost love in "Can't Let Go" serves to send the listener on a musical journey filled with varying emotions. Los Angeles Times editor Dennis Hunt wrote that in this song Mariah is playing a wounded lover. Rob Tannenbaum of Rolling Stone wrote that "moody grandeur" of this song will sound great on radio.

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