Tsuda Sen (津田 仙, August 6, 1837 – April 24, 1908) was a politician, educator and writer in Meiji period Japan.

He was hired by the Tokugawa bakufu as an interpreter, and accompanied Fukuzawa Yukichi on a mission to purchase warships in the United States in 1867.

He also spent time with the Hokkaido Colonization Office, where he made close contacts with future Prime Minister Kuroda Kiyotaka.

In 1873 Tsuda attended the Vienna Expo, where he met Sano Tsunetami (founder of the Japanese Red Cross), and where he received a lesson on Western agricultural techniques, particularly artificial crop pollination.

A supporter of agrarian rights, he was involved in the Ashio Copper Mine Scandal, one of Japan's first environmental disputes.