Nathaniel Walcott (born March 6, 1978) is an American musician, composer and arranger. He is a member of the band Bright Eyes, and has played in Conor Oberst's Mystic Valley Band and with singer-songwriter M. Ward. Between 2016 and 2019, Walcott was the touring pianist and keyboard player for the Red Hot Chili Peppers, during their The Getaway World Tour.

Walcott has also toured with the likes of the James Mercer and Danger Mouse-led group Broken Bells, Rilo Kiley, and the Glenn Miller Orchestra. In the studio, he has performed on the albums of such artists as Phoebe Bridgers, She & Him, U2, Beck, Jason Mraz, Maroon 5, and the Shins and has contributed arrangements to artists such as Mavis Staples, Angel Olsen, First Aid Kit, Jenny Lewis, Rilo Kiley, Pete Yorn, Cursive, and The Faint. He has also composed the scores for films such as The Fault in Our Stars and Regretting You.

Walcott was born on March 6, 1978, in Albany, New York. While he was a young child, his family moved to the Central New York village of East Homer. When Walcott was eight, his family moved to Lincoln, Nebraska.

While a high school student in Lincoln, Walcott played in several Lincoln-based bands, including Kid Quarkstar, with longtime friend and future Maroon 5 guitarist James Valentine. He also met musicians Mike Mogis, A.J. Mogis, and Ted Stevens of Lincoln-based band Lullaby for the Working Class, with whom he recorded and toured.

After graduating from high school in 1996, Walcott went on to attend DePaul University in Chicago. He took time off from his studies to tour both with The Glenn Miller Orchestra and Lullaby for the Working Class.

After university, Walcott engaged in freelance recording, arranging, and performing work with a very wide variety of artists including the Chicago-based groups Las Guitarras de Espana, the Mighty Blue Kings, and Pinetop Seven. He was also active in the improvisational and "experimental" music scene, performing with the likes of David Boykin, Mike Reed, and Keefe Jackson at such places as Fred Anderson's Velvet Lounge, the Hungry Brain, and the Green Mill, and also led his own group, the Nate Walcott Octet. While living in Chicago, both in college and after, Walcott remained connected to Nebraska, working as an arranger and player on records being produced by Mike Mogis for artists such as The Faint, Rilo Kiley, and Johnathan Rice.

While still a student and collaborating with musicians in the vibrant Lincoln and Omaha music scenes, Walcott met singer-songwriter Conor Oberst of the bands Bright Eyes, Commander Venus, and Desaparecidos. Walcott joined Bright Eyes on its tour in support of 2002's album Lifted or The Story is in the Soil, Keep Your Ear to the Ground and also on most subsequent tours after the "Lifted" tour. Walcott played on 2005's studio recordings I'm Wide Awake, It's Morning and Digital Ash in a Digital Urn and the live album Motion Sickness.

In 2006, in preparation for writing and recording Bright Eyes' next album, Walcott, along with Mike Mogis, was named a permanent member of the group. Cassadaga was released on April 10, 2007. Walcott co-wrote "Coat Check Dream Song." Following a five-month tour of the United States, Walcott wrote the arrangements for the band's appearance at the Hollywood Bowl with the Los Angeles Philharmonic Orchestra.