Futabatei Shimei (Japanese: 二葉亭四迷, 28 February 1864–10 May 1909) was a Japanese author, translator, and literary critic. Born Hasegawa Tatsunosuke (長谷川辰之助) in Edo (now Tokyo), Futabatei's works are in the realist style popular in the mid- to late-19th century. His work Ukigumo (Floating Clouds, 1887) is widely hailed as Japan's first modern novel.
After quitting his studies at the Russian language department at the Tokyo School of Foreign Languages (東京外国語学校) in protest over administrative restructuring, Futabatei published the literary criticism Shōsetsu Sōron at the encouragement of the critic and author Tsubouchi Shōyō in 1886. Futabatei's first novel Ukigumo was never finished, but its realist style strongly influenced fellow authors in his day. Futabatei was accomplished in Russian and translated the work of Ivan Turgenev and other Russian realists into Japanese.
In 1902, he learned Esperanto in Russia. Returning to Japan in 1906, he published the first Japanese-Esperanto instruction book "世界語" Sekaigo.
The origin of his pen name is in the curse his father said when told by his son that he aspired to study literature: Kutabatte shimee (くたばってしめぇ), "Drop dead!".