Jan Leonard Groth (25 February 1946 – 27 August 2014) was a Norwegian musician. He was active from the early 1970s onwards. He was a member of the progressive rock band Aunt Mary, where he was lead singer and keyboardist. He later moved on to Christian rock, where he most notably sang rock versions of many preacher singer's songs. He was also a member of the band Just 4 Fun. At the 1991 Eurovision Song Contest, Just 4 Fun represented Norway and played the song "Mrs. Thompson".