Dadan Island (Chinese: 大膽島; pinyin: Dàdǎn dǎo, also written as 大擔島) is a small island in Taiwan Strait, along the coast of Mainland China. It is located approximately 12,000 m (7.5 mi) to the Southwest of Lesser Kinmen and approximately 4,400 m (14,400 ft) from Xiamen. The Republic of China (Taiwan) controls the island, which is administered by Kinmen County Government under Lieyu Township, Kinmen County, Fukien Province.
Since 1949, Dadan Island has several times become the battlefront of conflicts between the People's Liberation Army and the Republic of China Armed Forces. On 30 June 2014, the control of the island and surrounding islets was handed over from the Republic of China Armed Forces to the civilian under the Coast Guard Administration of Kinmen County Government.
The total surface area of Dadan Island is 0.97 km2 (0.37 sq mi). The northern and southern part of the island are more elevated than its central area, which contains a strip of sandy beach. The highest elevation on the island is 92 m (302 ft).
Dadan Island is the largest of a small group of islets which also includes Erdan Island (二擔島), Sandan Island (三擔島), Wudan Island (五擔島), Huzi Island (虎仔島), etc. They sit astride the entrance into the Xiamen Harbor from the Taiwan Strait.