Gregory Allen Kurstin (born May 14, 1969) is an American record producer, multi-instrumentalist, and songwriter. He has won nine Grammy Awards, including Producer of the Year, Non-Classical in 2017 and 2018, and contributed to five songs that peaked atop the Billboard Hot 100.

Kurstin worked closely with English singer Adele on her albums 25 (2015) and 30 (2021). He co-wrote and produced the former album's record-breaking lead single "Hello", as well as latter's lead single "Easy on Me," which entered the US Hot 100 five hours after its release, and broke all-time records on Spotify with 24 million plays within 24. Among others, he has worked with Kylie Minogue, Sia, Kelly Clarkson, Halsey, Jonas Brothers, Kendrick Lamar, Maren Morris, Beyoncé, Dido, Gorillaz, the Shins, Beck, Paul McCartney, Pink, Lily Allen, Harry Styles, Miley Cyrus, Liam Gallagher, Foo Fighters, PinkPantheress and Wolf Alice. He often plays guitar, bass, keyboards and drums, as well as engineers and programs his musical productions.

Kurstin began his career as a jazz pianist and later co-founded Geggy Tah. He worked with singer Inara George to form the indie pop duo the Bird and the Bee in 2004.

Kurstin was born in Los Angeles, California. He is Jewish. He started playing piano at age five. Soon after, he picked up guitar and bass. Kurstin joined his first band at the age of 11, and at 12 co-wrote "Crunchy Water", the B-side to classmate Dweezil Zappa's "My Mother Is a Space Cadet".

In high school, Kurstin focused on jazz piano. After graduation, he moved to New York to study with Charles Mingus' pianist Jaki Byard at The New School for Jazz and Contemporary Music. In addition to coursework, as a student Kurstin played with prominent jazz artists including Bobby Hutcherson, George Coleman, and Charles McPherson. He returned to Los Angeles to finish his degree, and graduated from the California Institute of the Arts with a BFA in 1992.

In a 2013 interview, Kurstin said that his education in jazz had played a vital role in his pop success. "It's still something I carry over into my pop music work. It's really important to me that the notes I'm choosing strike the right emotional chord."

Kurstin continued to perform with Hutcherson, Coleman, McPherson and others following his graduation. In 1994, he formed Geggy Tah with Tommy Jordan, whom he had met at an LA jam. A friend passed a demo they recorded on to David Byrne, who signed them to his label, Luaka Bop. "They incorporate so many disparate elements into their sound that one senses a new sensibility afoot", Byrne said in 1997.

Geggy Tah released their debut album Grand Opening in 1994; Kurstin played bass, clavinet, guitar, organ, piano, synthesizers and drums, and was credited as a songwriter, producer, programmer, and backup vocalist. In 1996 the band released Sacred Cow. It included the song "Whoever You Are", which became a hit in 2001, after it was used in a television spot for Mercedes-Benz. As the song ascended the charts, Geggy Tah released their final album, Into the Oh.