Ferdinand P. Siagian is a public health researcher with extensive experience at the Center for Health Research, Universitas Indonesia. His expertise includes qualitative research, HIV/AIDS, drug use, harm reduction, reproductive health, family planning, instrument development, and data analysis. He has served as a researcher, consultant, field coordinator, and training manager in projects with the Ministry of Health, BPOM, UNFPA, UNICEF, the Global Fund, Jalin Foundation, and other national and international partners.