Builth Wells Urban District, in Brecknockshire, was an urban district between 1894 and 1974. It was succeeded by Brecknock.
Further information, including details of the archives here https://web.archive.org/web/20160303231012/http://www.archiveswales.org.uk/anw/get_collection.php?inst_id=40&coll_id=11982&expand=.