Tony Markellis (born September 10, 1952; died April 29, 2021) was an American bassist, producer, author, and illustrator from Helena, Montana, who resided in Saratoga Springs, New York, until his death. Markellis was best known as the bass guitarist for the Trey Anastasio Band and various other groups led by Phish guitarist Trey Anastasio. He also appeared on numerous releases on Vermont folk label Philo.