Joseph Williams was a Cook Islands politician and physician who served as Prime Minister of the Cook Islands for four months in 1999. He is credited with having worked to prevent the spread of the tropical disease lymphatic filariasis (elephantiasis). He principally resided in Auckland, New Zealand, where he was medical director of the Mt Wellington Integrated Family Health Centre.

The prime minister of the Cook Islands is the head of government of the Cook Islands, a self-governing territory in free association with New Zealand. The office was established in 1965, when self-government was first granted to the islands. Originally, the title "Premier" was used, but this was replaced by the title of "Prime Minister" in 1981.