Mark Helias is an American double bass player and composer born in New Brunswick, New Jersey.
He started playing the double bass at the age of 20, and studied with Homer Mensch at Rutgers University from 1971 to 1974, then at Yale School of Music from 1974 to 1976. He teaches at Sarah Lawrence College, The New School, and SIM.
Helias has performed with a wide variety of musicians, first and foremost with trombonist Ray Anderson, with whom he led the ironic 1980s avant-funk band Slickaphonics, and a trio with Gerry Hemingway on drums, formed in the late 1970s, later named BassDrumBone. Helias has also performed with members of Ornette Coleman's band, Don Cherry, Dewey Redman, and Ed Blackwell, and with musicians affiliated with the AACM, such as Anthony Braxton and Muhal Richard Abrams.
Since 1984 Mark Helias has released twelve recordings under his own name and further albums leading the archetypal improvising trio Open Loose since the late 1990s. The group comprises Helias on bass, first Ellery Eskelin, then Tony Malaby on tenor saxophone and Tom Rainey on drums.