Title: It Ain't Me
Content:  The lyrics to "It Ain't Me" were written by Andrew Watt, Brian Lee and Ali Tamposi. With Watt previously working with Kygo, the DJ's manager Myles Shear contacted Watt for a session with Kygo which Watt also facilitated for Lee and Tamposi. During their session for "It Ain't Me", they initially found the track very poor, but were trying to salvage it. Kygo and Shear suggested that they continue working on the song. After Kygo and Shear had left, Tamposi told Watt and Lee to play guitar and "Fleetwood Mac it", spawning a 45-minute jam session as well as the demo 
Title: It Ain't Me
Content:  notes, bass, synthesizers, finger-snap claps and pan flute melodies. Gomez sings the track in a husky tone, while in the chorus her vocals are reduced to recurring syllables. The lyrics are nostalgic and narrate a past relationship ruined by alcoholism. In addition to reaching number one in Croatia, Lebanon, and Norway, the song attained top five peaks in Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Malaysia, the Netherlands, New Zealand, Poland, Portugal, Scotland, Slovakia, Sweden and Switzerland. It also reached the top 10 in Italy, Spain, the United Kingdom and the United States.
Title: It Ain't Me
Content:  "It Ain't Me" is a song by Norwegian DJ Kygo and American singer Selena Gomez. It was released by Interscope Records, Sony and Ultra on 16 February 2017 as the lead single from Kygo's debut extended play Stargazing (2017) and it appears as an international bonus track on Gomez's album, Rare (2020). The song was written by Kygo, Brian Lee, Ali Tamposi, Gomez and Andrew Watt. It was produced by Kygo, Watt and Louis Bell. An EDM, dance-pop, electropop and tropical house song, "It Ain't Me" comprises an acoustic guitar line, and a build-drop arrangement in its chorus featuring pulsing 
Title: It Ain't Me
Content:  introduces sidechained vocal chops of Gomez singing syllables and are accompanied by percussion instruments. "It Ain't Me" is a breakup song with a theme of nostalgia. The lyrics are about standing up for yourself in the face of a toxic relationship. Gomez narrates the regret of a previous relationship ruined by her former lover's habits of drinking and partying too often. The lyrics address alcoholism. Tamposi explained that "It Ain't Me" is about a woman finding the strength to walk away from a toxic relationship despite the pressure she receives from society to stand by her man. Although the lyrics are sombre, the song has a distinctly uplifting and empowering sound.
Title: It Ain't Me
Content:  An EDM, dance-pop, electropop and tropical house song, "It Ain't Me" is composed in the key of C Major and is set in the time signature of alla breve at a tempo of 100 beats per minute. Gomez's vocal range spans from the low note of G3 to the high note of E5, while the music follows the chord progression of Am–C–F–C–F–C–G. Later in the song, the piano plays in a chord progression of: Am–C–G–F–Am–C–G. The song carries a calm tone and a drop common in tropical house music, but is complemented by an equal measure of electronic and pop rock elements. The track starts with a folk-like acoustic guitar riff. 
Title: Ain't You
Content:  "Ain't You" is a song by American R&B singer K. Michelle. It was released on February 12, 2016, as the second single from her third studio album, More Issues Than Vogue (2016).
Title: What It Ain't
Content:  "What It Ain't" is a song recorded by American country music artist Josh Turner. It was released in April 2004 as the third single from the album Long Black Train. The song reached #31 on the Billboard Hot Country Singles & Tracks chart and was written by Tim Mensy and Monty Criswell.
Title: It's Not U It's Me
Content:  "It's Not U It's Me" (stylized in all lowercase) is a song by American singers Bea Miller and 6lack. Hollywood Records released it on March 1, 2019, as the intended lead single from Miller's upcoming third studio album. However, the album was scrapped.
Title: It's Not U It's Me
Content:  "It's Not U It's Me" is a synth-pop song written by Miller, Justin Tranter, Mary Weitz, Mike Sabath, and 6lack and produced by Mike Sabath. The song is about "working on oneself before trying to help someone else". Miller said in an interview with Bustle that she wanted to "write a self-love song that wasn't corny" with this song.
Title: It Ain't Me
Content:  In early February 2017, "It Ain't Me" was registered on the American Society of Composers, Authors and Publishers (ASCAP) database. Gomez first teased the single with two Instagram stories on 3 February 2017. The first teaser showed a half-profile of the singer with a black "X" over her mouth as a 10-second snippet plays with the lyrics, "I had a dream / we were back to 17 / summer nights and liberties / never growing up," while the second teaser was a snippet of the song's beat. Gomez later revealed the single's cover art and release date on Instagram on 13 February 2017, and shared three teasers of the song on Snapchat the following day. "It Ain't Me" was released for digital download by Interscope, Sony and Ultra Music on 17 February 2017 as the first single from Kygo's upcoming second studio album. Interscope was the primary label since it is Gomez's label. A remix of the song featuring actor Vin Diesel was released on Facebook on 18 February 2017. "It Ain't Me" was sent to contemporary hit radio in the US on 28 February 2017.

Question: who sings the song it ain't me?
Answer: Selena Gomez.
American singer Selena Gomez.