John Mehegan (June 6, 1920 – 1984) was a jazz pianist, lecturer and critic. Mehegan was born in Wethersfield, Connecticut, and began playing the piano at the age of five. He taught himself to play by matching his fingers to the notes played on a neighborhood player piano. His mother gave him violin lessons, but he preferred piano. In 1946, he was appointed head of the jazz department at the Metropolitan Music School in New York. He later held posts at the Juilliard School of Music and Yale University. He was the jazz critic for the New York Herald Tribune.

Mehegan played solo piano for many years at the "Composer's Lounge" and "Ambassador Grill and Lounge" in New York City, as well as the "River Cafe" in Brooklyn, NY. He also played at numerous clubs in Southwest Connecticut, where he lived and raised a family.

John had many students, and was good friends with several great jazz musicians. He used to help Art Tatum navigate the subway uptown to the Harlem jazz clubs. The Mehegan children (Tara, Sean, and Eben) remember a constant stream of jazz legends visiting their home in Westport, CT. Leonard Bernstein, Dave Brubeck, and Gerry Mulligan, to name a few, were fellow residents of Connecticut; jam sessions were not unusual, with various members sitting in as the day unfolded.

He authored numerous books on jazz, including the Jazz Improvisation series, which sets out the basic principles of jazz. These are published in seventeen languages and sold around the world.

The American composer Leonard Bernstein dedicated a piano composition to Mehegan in his Four Anniversaries collection published in 1948. Marked agitato: scherzando, the piece, For Johnny Mehegan, commemorates Mehegan's birthday, June 6, 1920.