John Popper (born March 29, 1967 in Cleveland, Ohio) is the frontman and a founding member of the jam band Blues Traveler. He performs harmonica and vocals. He is widely considered a harmonica virtuoso, and is listed by harmonica manufacturer Hohner as a "Featured Artist", an accolade reserved for only the best and most successful harmonica players.

He frequently works as a guest musician for other bands. He has known to have performed with Dave Matthews Band, Karl Denson, and even with the Hungarian Ambassador to the United States.

Popper also played on Pocket Full of Kryptonite, their most successful album. His harmonica music can be heard in the feature film Blues Brothers 2000 (in which Blues Traveler appears). His harmonica was also featured on "What Would You Say", the second track on the Dave Matthews Band album, Under the Table and Dreaming.

John Popper was obese for most of the band's history. After undergoing angioplasty surgery in July 1999, he continued to have health problems having weighed near 400 lbs. In 2000, he underwent gastric bypass surgery, which led to a dramatic weight reduction.

He is an outspoken supporter of the Libertarian Party .