John Williams (1796–1839) was an English lay missionary, active in the South Pacific. Born near London, England, he was trained as a foundry worker and mechanic. In 1816, the London Missionary Society commissioned him as a missionary.

In 1817, he voyaged to the Society Islands, establishing a station on the island of Raiatea. From there, he visited a number of the island chains. Williams returned to Britain in 1834 to supervise the printing of his translation of the New Testament into the Rarotongan language. He also published a "Narrative of Missionary Enterprises in the South Sea Islands", making a contribution to English understanding and popularity of the region.

He returned to the islands in 1837. Most of his missionary work and his delivery of a cultural message was very successful. While visiting the New Hebrides in November, 1839, he was killed and eaten by cannibals on the island of Erromango .