the esperanto museum and collection of planned languages (, ), commonly known as the esperanto museum, is a museum for esperanto and other constructed languages in vienna, austria. it was founded in 1927 by hofrat hugo steiner and was incorporated into the austrian national library as an independent collection in 1928. today, it is a museum, library, documentation center, and archive. it accommodates the largest collection of constructed languages in the world and a linguistic research library for language planning. its online catalogue is available online.