Nils Hilmer Lofgren (born June 21, 1951) is an American rock musician, recording artist, songwriter, and multi-instrumentalist. Along with his work as a solo artist, he has been a member of Bruce Springsteen's E Street Band since 1984, a member of Crazy Horse, and the founder and frontman of the band Grin. In 2014, Lofgren was inducted into the Rock and Roll Hall of Fame as a member of the E Street Band.

Lofgren was born in Chicago, Illinois, to an Italian mother from Nicosia, Sicily and a Swedish father. When he was a young child, the family moved to the Washington, D.C., suburb of Bethesda, Maryland. Lofgren's first instrument was classical accordion, beginning at age five, which he studied seriously for ten years. After studying classical music and jazz, throughout his youth, Lofgren switched his emphasis to rock music, and focused on the piano and the guitar. Although left-handed, Lofgren plays the guitar right-handed.

Lofgren attended Walter Johnson High School in Bethesda, Maryland, but dropped out in 1968 at age 17 to pursue his music career. He had been a competitive gymnast in high school, a skill that was used on stage later in his performing career and reflected in the name of his 1985 album, Flip.

In 1968, Lofgren formed the band Grin with bassist George Daly and drummer Bob Berberich. Daly and Berberich were former players in the DC band The Hangmen. The group played in venues throughout the Washington, D.C., area.

Lofgren met Neil Young while Young was performing at the Georgetown club the Cellar Door, and began a long association. Young invited Lofgren to come to California and the Grin trio (Lofgren, Daly and Berberich) drove out west and lived for some months at a home Young rented in Laurel Canyon, Los Angeles. Lofgren would eventually use his album credits from working with Young to land Grin a record deal in 1971.

Daly left the band early on to become a Columbia Records A&R executive and was replaced by bassist Bob Gordon, who remained through the release of four critically acclaimed albums from 1971 to 1974, with guitar as Lofgren's primary instrument. The single "White Lies" got heavy airplay on Washington, D.C.-area radio. Lofgren wrote the majority of the group's songs and often shared vocal duties with other members of the band (primarily drummer Bob Berberich). After the second album, he added brother Tom Lofgren as a rhythm guitarist. Grin were released by their record company due to disappointing sales.

Lofgren joined Neil Young at age 18 to play piano and guitar on the album After the Gold Rush. Lofgren maintained his musical relationship with Young, appearing as a part of the Santa Monica Flyers on Young's Tonight's the Night album and tour, and again on the Trans album and tour. He has also been a recurring member of Crazy Horse (1970–1971; 2018–present), appearing on their 1971 LP and contributing songs to their catalogue. In 2018, Lofgren re-joined Crazy Horse and along with the band performed on Young's 2019 album Colorado and 2021's Barn as well as on 2022's World Record.

In 2023, the current members of Crazy Horse, along with Young, released the album All Roads Lead Home under the name Molina, Talbot, Lofgren and Young.