Dan Takuma (團 琢磨, September 7, 1858 - March 5, 1932) was a Japanese businessman who was Director-General of Mitsui, one of the leading Japanese zaibatsu (family conglomerates). He was a graduate of Massachusetts Institute of Technology and was married to the younger sister of statesman Kaneko Kentarō.
Dan favored the cultivation of closer relations between Japan and the Western powers. In 1921, he led the Japanese Businessmen's Mission, in which a group of Japanese business leaders visited the United States, Great Britain, and France to discuss bilateral economic issues and to promote personal ties with businesspeople of those countries.
On March 5, 1932, Dan was assassinated by right-wing nationalist Goro Hishinuma as part of the League of Blood Incident.
Dan's son was embryologist Dan Katsuma, and his grandson was operatic composer Dan Ikuma.