Edgar von Wahl or Edgar de Wahl (born August 11, 1867 in Olwiopol, Russian Empire (now Pervomaisk, Mykolaiv Oblast, Ukraine); died in 1948 in Estonia) was a teacher and creator of the language Occidental. An Estonian of ethnic Baltic German origin, he studied in Saint Petersburg and spent most of his later professional life in Tallinn, Estonia.
At first an adherent of Volapük, de Wahl later became one of the first users of Esperanto and advised Ludwig Zamenhof on some points of grammar and vocabulary of that language. After several years he abandoned Esperanto, and in the following decades he worked on the problem of the ideal form of an international auxiliary language.
In 1922 he published a "key" to a new language, Occidental, and the first number of a periodical entitled Kosmoglott (later Cosmoglotta), written in that language. In following years, de Wahl participated in discussions about Occidental, and allowed the language to develop gradually as a result of the recommendations of its users. After World War II started in 1939, he had only intermittent contacts with the Occidentalist movement, which had become centered in Switzerland. He became a member of the Committee of Linguistic Advisors, part of the International Auxiliary Language Association, which would present Interlingua in 1951.
The last years of his life were spent in a sanatorium in Estonia, where he died in 1948.
The name of Occidental was changed to Interlingue in 1949. Today, the language is again most often called Occidental.