John Albert "Johnny" Guarnieri (March 23, 1917 – January 7, 1985) was an American jazz and stride pianist, born in New York City.
Guarnieri joined the George Hall orchestra in 1937. He is perhaps best known for his big band stints with Benny Goodman in 1939 and with Artie Shaw in 1940. Guarnieri is also noted for his embellishment and juxtaposition of jazz with classical piano, such as Scarlatti and Beethoven.
Throughout the 1940s Guarnieri was a busy sideman, recording with artists such as Charlie Christian, Cozy Cole, Ike Quebec, Charlie Kennedy, Hank D'Amico and Ben Webster. He also led his own group called the "Johnny Guarnieri Swing Men" and recorded with them on the Savoy label, a group that included Lester Young, Hank D'Amico, Billy Butterfield and Cozy Cole. He also led a trio in the 1940s composed of himself, Slam Stewart and Sammy Weiss, recording again for Savoy. During the 1940s he also recorded for the short-lived Majestic label, playing solo piano and with his trio.