Dr Mark O’Reilly completed his medical degree at the University of Newcastle in 2001 and was based at Princess Alexandra Hospital, Brisbane and St George Hospital, Sydney in his early years. After working in the UK for a year, he returned to Sydney and began training in Oncology and Palliative Care. He later decided General Practice and Sexual Health were a better fit, and completed GP training at 407 Doctors, before relocating with the team to East Sydney Doctors. He also completed a Masters in Public Health and Tropical Medicine through James Cook University in 2009.

In 2010, Mark moved to Melbourne and worked at Prahran Market Clinic for more than 12 years. During this time, he qualified as a Sexual Health Physician and was a director of the clinic for a number of years. He became a co-director at East Sydney/Bondi Road Doctors in early 2023 and at Taylor Square Private Clinic in mid-2023.

Mark is a clinical advisor to ASHM Health and a member of the Australian HIV antiretroviral guidelines committee. He also recently completed a 6-year term on the RACP Sexual Health Training committee. He attends HIV conferences and advisory boards regularly. Mark enjoys medical education and is frequently involved in organising and presenting at various conferences and events. He also teaches medical students and trains GPs in HIV medicine.

Current medical interests include HIV, viral hepatitis and STI treatment and prevention, HIV clinical trials and prevention and management of chronic health conditions.