Carl Hilding "Doc" Severinsen (born July 7, 1927) is an American retired jazz trumpeter who led the NBC Orchestra on The Tonight Show Starring Johnny Carson.

Severinsen was born in Arlington, Oregon, to Minnie Mae (1897–1998) and Carl Severinsen (1898–1972). He was nicknamed Doc after his father, the only dentist in Arlington, who was born in Germany to a Danish father and a Swiss mother. Severinsen's father played violin and wanted him to play it, as well, but Severinsen wanted to play trombone. Because his arms were not long enough for trombone, and the small Arlington music store had none available, he settled for the cornet. A neighbor provided him with some lessons, while his father, tobacco in mouth, instructed him to spit out the notes like spitting tobacco. His mother threatened to spank him if he did not practice. Growing up, Severinsen idolized trumpeter and band leader Harry James.

Severinsen proved to have a knack for the instrument and was in a high-school band when he was seven. At 9, he won a state trumpet contest, at 12 he won the Music Teachers National Association’s national contest, at 13, he joined a multistate all-star band, and at 14, he auditioned for Tommy Dorsey, but was not hired. He started a quartet called the Blue Notes that performed at local dances.

Before graduating from high school, he was hired to go on the road with the Ted Fio Rito Orchestra. After graduation, he went on tour with Charlie Barnet, Tommy Dorsey, and Benny Goodman. He served in the Army during World War II. Severinsen was a member of Sam Donahue's band between 1946 and 1951. In 1946, he played trumpet on radio station KODL.

In 1949, Severinsen landed a job as a studio musician for NBC, where he accompanied Steve Allen, Eddie Fisher, Dinah Shore, and Kate Smith, was a member of the original band for Tonight Starring Steve Allen, and was the soloist playing the closing theme. He left the show with Allen in 1957. The leader of the Tonight Show Band, Skitch Henderson, asked him to return as first-chair trumpeter in 1962 for what had become The Tonight Show Starring Johnny Carson, and five years later, after Milton Delugg, Severinsen was leading the band.

Under Severinsen's direction, the Tonight Show Band, styled the NBC Orchestra, became perhaps the best known big band in America. Severinsen became one of the most popular bandleaders, appearing almost every night on television. He led the band during commercials and while guests were introduced. He joked with Johnny Carson, the show's host, and developed an amusing habit of wearing gaudy clothing.

The show introduced a comic "Stump the Band" segment in which audience members called out the titles of obscure songs to see if the band could play them. Severinsen often cried "key of E", his signal for the band to strike up a Western theme, and then he would enthusiastically sing a country music-flavored nonsense song.

Severinsen substituted for Ed McMahon on occasions when Ed was absent as Carson's announcer and sidekick. He typically assumed this role when the show featured a guest host, which became increasingly frequent during the program's later years. Tommy Newsom was usually the band's substitute director when Severinsen was away from the show or filling in for McMahon. The sidekick role was omitted from the show when Leno guest hosted (it was discontinued altogether after Leno replaced Carson permanently). While Leno guest hosted for Carson, Severinsen typically introduced Leno and led the band while interacting with Leno in a similar manner to his interactions with Carson and McMahon.