Esperanto is the most widely spoken constructed international auxiliary language. It was created by Polish ophthalmologist L. L. Zamenhof in 1887, when he published a book detailing the language, Unua Libro ("First Book"), under the pseudonym "Dr. Esperanto". The word esperanto translates into English as "one who hopes".

Zamenhof's goal was to create an easy and flexible language that would serve as a universal second language to foster world peace and international understanding, and to build a community of speakers, as he believed that one could not have a language without such a community.

His original title for the language was simply "the international language" (lingvo internacia), but early speakers grew fond of the name Esperanto and began to use it as the name for the language just two years after its creation; the name quickly gained prominence and has been used as an official name ever since.