Lars Ulrich (/ˈʊlrɪk/ ^ⓘ; Danish: [ˈlɑːs ˈulˀʁek]; born 26 December 1963) is a Danish musician who is the drummer and a founding member of American heavy metal band Metallica. Along with James Hetfield, Ulrich has songwriting credits on almost all of the band's songs, and the two of them are the only remaining original members of the band.

The son and grandson respectively of tennis players Torben and Einer Ulrich, he played tennis in his youth and moved to Los Angeles at age 16 to train professionally. However, rather than playing tennis, Ulrich began playing drums. After publishing an advertisement in The Recycler, Ulrich met Hetfield and formed Metallica.

Ulrich was born on 26 December 1963 into an upper-middle-class family in Gentofte, Denmark; the son of Lone (née Sylvester-Hvid) and tennis player Torben Ulrich. The family lived at Lundevangsvej 12 in Hellerup. His paternal grandfather was tennis player Einer Ulrich. His paternal grandmother, Ulla Meyer, was from a Jewish family; as a result, Ulrich's grandfather was persecuted by the Nazis during World War II. Saxophonist Dexter Gordon was Ulrich's godfather, and he is a childhood friend of musician Neneh Cherry.

In February 1973, Ulrich's father obtained passes for five of his friends to a Deep Purple concert held in the same Copenhagen stadium as one of his tennis tournaments. When one of the friends could not go, they gave their ticket to the nine-year-old Lars, who was mesmerized by the performance and bought the band's album Fireball the next day. The concert and album had a considerable impact on Ulrich, inspiring the start of his music career.

As a result of his newfound interest in music, he received his first drum kit, a Ludwig, from his grandmother around the age of 12 or 13. Ulrich originally intended to follow in his father's footsteps and play tennis, and he moved to Newport Beach, California, in the summer of 1980. Despite being ranked in the top ten tennis players of his age group in Denmark, Ulrich failed to make it into the seven man Corona del Mar High School tennis team, contributing to his decision to focus on music.

In the documentary Anvil! The Story of Anvil, Ulrich said that attending a Y&T show was his defining moment in wanting to become a musician. In 1981, he discovered British heavy metal band Diamond Head. He was excited about the band's style of music after purchasing their album Lightning to the Nations, and traveled from San Francisco to London to see the band perform at the Woolwich Odeon. Ulrich remains a fan of Diamond Head and would later mix their album The Best of Diamond Head. Upon returning to the U.S., Ulrich placed an advert in a local newspaper looking for musicians to start a band with him. James Hetfield responded, and Metallica was formed.

Later in 1981, Ulrich met James Hetfield in Downey, California, and they formed the heavy metal band Metallica upon Ulrich securing a spot in a compilation album of local metal bands named Metal Massacre. He got the band name from a friend, Ron Quintana, who was brainstorming names for a heavy metal fanzine he was creating, with Metallica and Metal Mania being among the options; Ulrich encouraged him to choose Metal Mania, and used the name Metallica for himself.

He became known as a pioneer of fast thrash drum beats, featured on many of Metallica's early songs, such as "Metal Militia" from Kill 'Em All, "Fight Fire with Fire" from Ride the Lightning, "Battery" and "Damage Inc." from Master of Puppets and "Dyers Eve" from ...And Justice for All. He has since been considerably influential due to both the popularity of his band, as well as his drum techniques, such as the double bass drum in the song "One" (...And Justice for All) and "Dyers Eve". Since the release of Metallica, Ulrich adopted a less focused and simplified style of drumming, and reduced his kit from a 9-piece to a 7-piece.