Kazimierz Bein (1872 – 15 June 1959), often referred to by his pseudonym Kabe,[1] was a Polish ophthalmologist, the founder and sometime director of the Warsaw Ophthalmic Institute (Warszawski Instytut Oftalmiczny).

As a young man, Bein participated in the Polish movement for independence from Russia, for which he was exiled for several years; thus he was forced to finish his medical training in Kazan.

Bein became an eminent pioneer of Esperanto prose, writing under the pseudonym, "Kabe," an abbreviation of his actual name (and also the Polish pronunciation of his initials, "K.B.").

In 1904 he gained fame with his translation of a 1900 novel by Wacław Sieroszewski, Dno nędzy (The Depths of Misery; Esperanto title: Fundo de l' Mizero).

Shortly after he left the movement, Esperantists coined the word kabei,[2] after "Kabe," meaning "to fervently and successfully participate in Esperanto, then suddenly and silently drop out."