Jack K. Pleis (May 11, 1917 – December 5, 1990) was an influential American jazz pianist, arranger, conductor, composer, and producer. Born in Philadelphia, Pennsylvania, Pleis began his classical piano training at the age of four and performed in concert by the age of seven. His early exposure to music continued with appearances on children's radio programs by age eleven. Initially enrolling in college with the intention of studying medicine, Pleis supported his studies by playing piano in jazz and popular music bands, eventually leaving school to pursue a musical career in New York City.

In New York, Pleis became a successful pianist, arranger, conductor, and composer. He was part of Jan Savitt's Top Hatters before enlisting in the Army during World War II. Post-war, he formed the Jack Pleis Trio and worked at RCA Victor studios. His orchestra backed artists like Teresa Brewer and Bobby Wayne, contributing to Brewer's hit "Music! Music! Music!" in 1949.

Pleis joined the American Society of Composers, Authors and Publishers (ASCAP) in 1950 and began working at London Records under Tutti Camarata. He released his own singles and worked with artists such as Ralph Young and Snooky Lanson. In June 1950, Pleis married Eve Young, a London recording artist, and they had a daughter, Michelle, in 1951.

Pleis's career continued to flourish as he worked with various artists, including The Bell Sisters and Teresa Brewer. His wife, Eve, later signed with Coral Records under the name Karen Chandler, achieving success with "Hold Me, Thrill Me, Kiss Me," backed by Pleis's orchestra.

Throughout his career, Pleis arranged over 150 songs and collaborated with notable artists like Louis Armstrong, Harry Belafonte, Bing Crosby, Sammy Davis Jr., Benny Goodman, Earl Grant, Brenda Lee, and Joe Williams. He recorded with London and Decca Records in the 1950s and Columbia Records in the 1960s. Jack Pleis passed away in Palm Springs, California, at the age of 73.