Pra-Esperanto ('primordial Esperanto' in the language itself) is the modern term for any of the various language projects created by L. L. Zamenhof prior to the publication of his Unua Libro de Esperanto.

As a child, Zamenhof had the idea to introduce an international language for communication between different language groups. He originally wanted to revive some form of simplified Latin or Greek, but as he grew older he realised that it would be better to create a new language for the purpose. During his teenage years he worked on the project until he thought the language ready for public demonstration. On December 17, 1878 (that is, about one year before the first publication of Volapük), Zamenhof celebrated his birthday and the birth of the language with some friends, who liked the project. Zamenhof himself called his language "Lingwe Uniwersala" ("universal language").

While at university, Zamenhof handed his work over to his father, Mordechai, for safe-keeping until he had completed his medical studies. His father, not understanding the ideas of his son and thinking the project a pointless effort, burned the work. Zamenhof didn't find out about this until 1881. Bravely, he restarted work to prepare a new language textbook.

We have now only four lines of the language from 1878, from an early song that Zamenhof composed:

 Malamikete de las nacjes,          Emnity of the nations,
 Cadó, Cadó, jam temp' está;        Fall, Fall, it is already time!;
 La tot' homoze in familje          All humanity in [one] family
 Konunigare so debá.                Must unite itself.
During later years, Zamenhof remade, modified, and refined his language idea, mostly through translation into and out of other languages.

Through different versions and attempts at the language, Zamenhof changed certain features, e.g.:

  • Variable syllable accents, for certain forms of verbs, were rejected in favour of allways stressing the second-last.
  • The letters ĉ, ĝ, etc. replaced the Polish ć, dź, etc.

By 1885, the language was greatly changed, but it still remained somewhat similar to how it looked at the start. In a later letter to Nikolai Borovko, Zamenhof wrote:
"I worked for six years perfecting and testing the language, when in the year 1878 the language had seemed already completely ready to me."

In 1887, Zamenhof published the "Unua Libro" ("The First Book"), which contained the Esperanto language now in existence.

Gaston Waringhien, in his book "Lingvo kaj vivo" ("Language and Life"), analyzed the evolution throughout the manuscripts from 1881, 1882, and 1885.