Joseph Marie Albert "Joep" Lange (25 September 1954 – 17 July 2014) was a Dutch medical doctor and researcher. He mainly worked in HIV therapy. He served as the President of the International AIDS Society (IAS) from 2002 to 2004. He was also the Founding Chairman of PharmAccess Foundation until his death in 2014. The IAS has 16,000 members from 196 countries.