- SAARC
- see South Asian Association for Regional Cooperation (1985 - ) - SAATHI
- see Solidarity and Action Against the HIV Infection in India (2000 - ) - Safety of blood supply
- see Blood safety - Samoa, Independent State of Samoa
- Samoa, American
- see American Samoa, Territory of American Samoa - Save the Children Australia
- Save the Children International Alliance
- see International Save the Children Alliance (1997 - ) - Save the Children UK (1919 - )
- School of Public Health, La Trobe University
- School of Public Health and Community Medicine (2002 - ), The University of New South Wales
- Schools
- Seafarers
- see Mobile populations - SEAMEO
- see Southeast Asian Ministers of Education Organization (1965 - ) - The Secretariat of the Pacific Community (1947 - )
- Security and HIV/AIDS
- Seven Sisters (2001 - )
- Seventh International Congress on AIDS in Asia and the Pacific (2005)
- Sex education
- see Education - Sex workers and clients
- Sexuality
- Sexually transmitted diseases
- see Sexually transmitted infections - Sexually transmitted infections
- Sida
- see Swedish International Development Cooperation Agency - SINAC
- see Solomon Islands National AIDS Council (2004 - ) - Singapore, Republic of Singapore
- Sixth International Congress on AIDS in Asia and the Pacific (2001)
- SMARTWork Project
- Social Determinants
- see Determinants of the epidemic - Socialist Republic of Vietnam, Vietnam
- Solidarity and Action Against the HIV Infection in India (2000 - )
- Solomon Islands
- Solomon Islands National AIDS Council (2004 - )
- Soros Foundation
- see Open Society Institute (1993 - ) - South Asia
- South Asian Association for Regional Cooperation (1985 - )
- South Korea
- see Korea, Rep., Republic of Korea - South Pacific
- South-East Asia
- Southeast Asian Ministers of Education Organization (1965 - )
- SPC
- see The Secretariat of the Pacific Community (1947 - ) - Special Administrative Regions of the People's Republic of China, Hong Kong
- Spiritia
- see Spiritia Foundation (1995 - ) - Spiritia Foundation (1995 - )
- Sri Lanka, Democratic Socialist Republic of Sri Lanka
- St. Vincent's Institute of Medical Research, National Serology Reference Laboratory, Australia (1985 - )
- STI
- see Sexually transmitted infections - Stigma and discrimination
- Strategic planning and management
- Strategic plans
- see National plans - Street Friends
- see Mith Samlanh (1994 - ) - Support
- see Care and support - Surveillance
- see Behavioural surveillance - Surveillance
- see Epidemiological surveillance - Swedish International Development Cooperation Agency