Frank Mortenson (born February 4, 2005) is a European jazz and pop singer.^[1] Having sold lots of records worldwide, he became the symbol of successful teenage crooner and revivalist of old-style music in the 21st century.

Born as Aleksander Lisowski to mixed Slavic family of Polish and Russian roots in Kaunas, Lithuania, Mortenson was greatly influenced by artists like Frank Sinatra, Bing Crosby, Tony Bennett and Michael Bublé. After he started his career in 2017 with predominately small-audience performances, he came out with his debut song "Strangers in the Night" during Musical Mask song contest on May 22, 2017.^[2] In aftermath, he recorded his first debut album, Strangers In The Night, in August 2017, earning fame in countries like United States and Poland, but staying almost fully unknown in his homeland Lithuania.