Michael Trent Reznor (born May 17, 1965) is an American singer, songwriter, musician, and composer. He came to prominence as the founder, lead singer, multi-instrumentalist, and primary songwriter of the industrial rock band Nine Inch Nails. The band's line-up has constantly changed, with Reznor being its only official member from its creation in 1988 until 2016, when he added English musician and frequent collaborator Atticus Ross as its second permanent member.

Reznor began his career in 1982 as a member of synth-pop bands such as The Innocent, Slam Bamboo, and Exotic Birds. The first Nine Inch Nails album, Pretty Hate Machine (1989), was a moderate success but largely remained popular with underground audiences; the next two albums, The Downward Spiral (1994) and The Fragile (1999), brought the band widespread critical acclaim. There have since been eight more Nine Inch Nails albums and six EPs. Reznor has also contributed to the work of artists such as his protégé Marilyn Manson, rapper Saul Williams, and pop singer Halsey. Alongside his wife Mariqueen Maandig and long-time collaborators Atticus Ross and Rob Sheridan, he formed the post-industrial group How to Destroy Angels in 2009.

Since 2010, Reznor and Ross have worked on numerous film and television scores, most notably for movies directed by David Fincher and Luca Guadagnino. These include Fincher's The Social Network (2010), The Girl with the Dragon Tattoo (2011), and Gone Girl (2014), as well as Guadagnino's Bones and All (2022), Challengers (2024), and Queer (2024). Reznor and Ross won the Academy Award for Best Original Score for The Social Network and Soul (2020) and the Grammy Award for Best Score Soundtrack for Visual Media for The Girl with the Dragon Tattoo and Soul, sharing both awards for Soul with co-composer Jon Batiste. Reznor and Ross won the Primetime Emmy Award for Outstanding Music Composition for a Limited Series for Watchmen (2019). The pair also scored Ken Burns's 10-part documentary The Vietnam War (2017).

Michael Trent Reznor was born in New Castle, Pennsylvania, on May 17, 1965, the son of Nancy Lou (née Clark) and Michael Reznor. He is of German and Irish descent, and grew up in Mercer. His great-grandfather, George Reznor, founded the heating and air conditioning manufacturer Reznor Company in 1884. After his parents divorced when he was six years old, Reznor's sister Tera lived with their mother while he went to live with his maternal grandparents. He began playing the piano at the age of 12 and showed an early aptitude for music. His grandfather told People in February 1995, "He was a good kid [...] a Boy Scout who loved to skateboard, build model planes, and play the piano. Music was his life, from the time he was a wee boy. He was so gifted."

Reznor has acknowledged that his sheltered life left him feeling isolated from the outside world. In a September 1994 interview with Rolling Stone, he said of his career choices, "I don't know why I want to do these things, other than my desire to escape from Small Town, U.S.A., to dismiss the boundaries, to explore. It isn't a bad place where I grew up, but there was nothing going on but the cornfields. My life experience came from watching movies, watching TV and reading books and looking at magazines. And when your culture comes from watching TV every day, you're bombarded with images of things that seem cool, places that seem interesting, people who have jobs and careers and opportunities. None of that happened where I was. You're almost taught to realize it's not for you." However, in April 1995, he told Details that he did not "want to give the impression it was a miserable childhood".

Reznor would later recall, "The first concert I ever saw was the Eagles in 1976. The excitement of the night struck a chord with me and I remember thinking, 'Someday I'd love to be up on that stage.'" At Mercer Area Junior/Senior High School, he learned to play the tenor saxophone and tuba, and was a member of both the jazz band and marching band. The school's former band director remembered him as "very upbeat and friendly". He became involved in theater while in high school, being awarded the "Best in Drama" accolade by his classmates for his roles as Judas in Jesus Christ Superstar and Professor Harold Hill in The Music Man. He graduated in 1983 and enrolled at Allegheny College in Meadville, where he studied computer engineering.

While still in high school, Reznor joined local band Option 30 and played three shows a week with them. After a year of college, he dropped out to pursue a career in music in Cleveland, Ohio. His first band in Cleveland was the Urge, a cover band. In 1985, he joined The Innocent as a keyboardist; they released one album, Livin' in the Street, but Reznor left the band after three months. In 1986, he joined local band Exotic Birds and appeared with them as a fictional band called The Problems in the 1987 film Light of Day. During this time, Reznor also contributed on keyboards to the band Slam Bamboo and briefly joined the new wave band Lucky Pierre.

Reznor got a job at Cleveland's Right Track Studio as an assistant engineer and janitor. Studio owner Bart Koster later commented, "He is so focused in everything he does. When that guy waxed the floor, it looked great." Reznor asked Koster for permission to record demos of his own songs for free during unused studio time. Koster agreed, remarking that it cost him "just a little wear on [his] tape heads".