The English word antidisestablishmentarianism (UK Listeni/ˌæn.ti.dɪz.əs.tæb.lɪʃ.mənˈtɛə.rɪə.nɪ.zᵊm/, US Listeni/ˌæn.taɪˌdɪs.ɛsˌtæb.lɪʃ.məntˈɛ.ri.ənˌɪ.zm/) is notable for its unusual length of 28 letters and 12 syllables, and is one of the longest words in the English language. It has been cited as the longest word in the English language, excluding coined and technical terms.

The word became known in the public realm in the United States via a popular television show in the 1950s, The $64,000 Question, when a young contestant correctly spelled it to win. A slightly longer, but less commonly accepted, variant of the word can be found in the Duke Ellington song "You're Just an Old Antidisestablishmentarianismist;" although, the correct construction of the word used in the song should be "antidisestablishmentarianist" (without the "ism"), or "antidisestablishmentarian." The word is also used by Eminem in his song "Almost Famous."