Allen Kelsey Grammer (born February 21, 1955) is an American actor, producer, and singer. He rose to fame for his role as psychiatrist Dr. Frasier Crane in the NBC sitcom Cheers (1984–1993) and its spin-off Frasier (1993–2004, and again from 2023 to 2024). With more than 20 years on the air, it is one of the longest-running roles played by a single actor in primetime television history. He has received numerous awards, including a total of six Emmy Awards, three Golden Globe Awards, a Screen Actors Guild Award, and a Tony Award.

Grammer, who trained in acting at the Juilliard School and the Old Globe Theatre, made his professional debut as Lennox in a Broadway revival of Macbeth in 1981. The following year he played Cassio in Othello alongside Christopher Plummer and James Earl Jones. In mid-1983 he appeared with Mandy Patinkin in the original off-Broadway production of Stephen Sondheim's musical Sunday in the Park with George. Since then he has starred in productions of Sweeney Todd: The Demon Barber of Fleet Street, My Fair Lady, Big Fish, and Finding Neverland.

In film he is known for his role as Dr. Hank McCoy / Beast in the superhero films X-Men: The Last Stand (2006), X-Men: Days of Future Past (2014), and The Marvels (2023). Other roles include Down Periscope (1996), The Pentagon Wars (1998), and All the King's Men (2008). He is also known for his voice work in Anastasia (1997) and Toy Story 2 (1999), and for his role as Sideshow Bob in The Simpsons (1990–present). He has made guest appearances in the sitcoms 30 Rock (2010–2012), The Unbreakable Kimmy Schmidt (2016), and Modern Family (2017). For his role as a corrupt mayor in the Starz political series Boss (2011–2012), he won a Golden Globe Award for Best Actor in a Drama Television Series.

In early 2010 Grammer returned to Broadway in the musical revival La Cage aux Folles, for which he received a Tony Award nomination for Best Actor in a Musical. In mid-2016 Grammer won a Tony Award for Best Musical as a producer of the revival of the musical The Color Purple. In early 2019 he played Don Quixote in a production of Man of La Mancha at the London Coliseum. In late 2023 The Telegraph named Grammer one of the "best actors" of his generation. On May 22, 2001, he was honored with a star on the Hollywood Walk of Fame.