Mark M. Phillips (born March 31, 1951) is an American astronomer who works on the observational studies of all classes of supernovae.

He has worked on SN 1986G,[1] SN 1987A,[2] the Calán/Tololo Supernova Survey, the High-Z Supernova Search Team, and the Phillips relationship.

[3][4] This relationship has allowed the use of Type Ia supernovae as standard candles, leading to the precise measurements of the Hubble constant H0[5][6] and the deceleration parameter q0,[7] the latter implying the existence of dark energy or a cosmological constant in the Universe.

He received his undergraduate degree in Astronomy from San Diego State University in 1973, and his Ph.D., also in Astronomy & Astrophysics in 1977, from the University of California, Santa Cruz and Lick Observatory where he was a student of Professor Donald Osterbrock.

After graduate school, he was a postdoc at CTIO, then at Anglo-Australian Observatory, moving back to Chile in 1982 to become a staff astronomer at CTIO.