Men Behind the Sun (Chinese: 黑太阳731 / 黑太陽731; pinyin: hēi tài yáng 731, literally meaning "Black Sun: 731") is a 1988 war-based horror movie. When it was released, the movie was rated III under the Hong Kong rating system (similar to the United States MPAA rating NC-17). The movie is about Unit 731, a Japanese biological and chemical warfare research and development unit which operated during the Second Sino-Japanese War (World War II) with graphic materials. It was banned in some countries.

In Australia, it was refused classification. It was later rerated R18 on appeal.

In the United States, the movie was released without a rating.

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