Pneumonoultramicroscopicsilicovolcanoconiosis (Listeni/njuːˌmɒnoʊˌʌltrəmaɪkrɵˌskɒpɪkˌsɪlɪkoʊvɒlˌkeɪnɵkɒnaɪˈoʊsɪs/) is an English word that refers to a lung disease that is otherwise known as silicosis. It is the longest word in the English language published in a dictionary, the Oxford English Dictionary.

According to the Oxford English Dictionary, it is "an artificial long word said to mean a lung disease caused by inhaling very fine ash and sand dust."