"I'm Not the Only One" is a popular song by British singer-songwriter Sam Smith. It was released as the fourth single from his debut studio album, "In the Lonely Hour," in 2014.

"I'm Not the Only One" is a soulful and emotive ballad that showcases Sam Smith's powerful and soulful vocals. The song's lyrics narrate the story of a person who discovers their partner is being unfaithful, realizing they are not the only one in their lover's life. The song explores themes of heartbreak, betrayal, and the pain of realizing a relationship is not as strong as they had believed.

The song was written by Sam Smith and James Napier, with production by Jimmy Napes and Steve Fitzmaurice.

Upon its release, "I'm Not the Only One" achieved commercial success and critical acclaim. It received widespread praise for Sam Smith's vocal performance and the emotional depth of the song. The soulful and heartrending nature of the track resonated with audiences, making it one of the standout songs from "In the Lonely Hour."

The music video for "I'm Not the Only One" features a storyline about a woman who discovers her husband's infidelity and confronts him. The video's emotional visuals complement the song's themes of betrayal and heartache.

"I'm Not the Only One" received positive reviews from music critics, who praised its emotional and vulnerable lyrics, as well as Sam Smith's vocal delivery.

Over time, "I'm Not the Only One" has remained a beloved and iconic song in Sam Smith's discography. Its soulful and heartfelt sound, Sam Smith's powerful vocals, and its exploration of the pain of infidelity and heartbreak have made it a timeless ballad, capturing the essence of emotional vulnerability in love and relationships.