Onllwyn (Welsh pronunciation: [ˈɔnɬʊɨn]) is a small village and community in Neath Port Talbot, Wales, near Seven Sisters.

Musical performances took place at Onllwyn Miners' Welfare Hall in 1976, including one by The Strange Creek Singers featuring American musicians Hazel Dickens, Alice Gerrard, Mike Seeger, Tracy Schwartz, and Lamar Grier.

The movie chronicles the true story of a group of lesbian and gay activists who raised money to help families affected by the British miners' strike in 1984.

There is a Community College, "Dove Workshops", village shop, post office, pub, and association football and rugby union teams.

Onllwyn was bounded by the wards of Abercraf and Tawe Uchaf (both in Powys) to the north; Glynneath to the southeast; and Seven Sisters to the south west.