Sơn Ngọc Thành (Khmer: សឺង ង៉ុកថាញ់; 7 December 1908 – 8 August 1977) was a Cambodian nationalist and republican politician, with a long history as a rebel leader and (for brief periods) a government minister.

The political outlook of Nagaravatta, which urged Khmers to break the commercial monopoly of foreign traders by starting their own businesses, was to make Thanh and his colleagues receptive to Japanese fascism, or as he termed it, "National Socialism".

[3] Thanh's ideology was essentially republican, right-wing, and modernising in outlook, which was to make him a longstanding opponent of the King Norodom Sihanouk.

After demonstrations against the French in July 1942, Thanh fled to Japan, returning when Sihanouk declared Cambodia's independence on 12 March 1945, during the Japanese occupation.

In 1952, accompanied by his lieutenant Ea Sichau (a French-educated customs official and leftist intellectual) and a number of supporters, Thanh disappeared into the forests in the area of Siem Reap, and began to organise resistance.