Marcus Augustine Conant (born May 11, 1936, in Jacksonville, Florida) is an American dermatologist and one of the first physicians to diagnose and treat Acquired Immune Deficiency Syndrome (AIDS) in 1981.

[2] When his father was deployed to Europe, Marcus and his family moved back to Jacksonville, Florida where he attended high school.

As a resident at UCSF, Conant also volunteered at the Haight Ashbury Free Clinics, where he treated patients with genital herpes.

[10] [11] In 2010, Conant closed his practice in San Francisco, where he cared for over 8,000 patients with HIV/AIDS, and moved to New York, citing rising costs and difficulties in dealing with health insurance companies.

[13] Conant was eventually moved up to the role of Chief Medical Officer (CMO) at American Gene Technologies in October 2021, where he oversees the clinical trials for AGT's potential HIV cure therapy, AGT103-T.[14]