The walls of Zuwila constitute one of the most impressive defensive enceintes among Libyan Saharan oasis towns, but hitherto their construction date has been uncertain. A new AMS radiocarbon date now offers the strongest support for an association with the establishment of the Banu Khattab dynasty at Zuwila in the early tenth century AD, as some previous commentators had suspected. The walls relate to a fortress of approximately 4.5 hectares built on the north flank of an already long-established Saharan town. No detailed account of these walls has ever been published before, though Charles Daniels did carry out a survey of them in 1968 and a summary description was included in the work of the Fazzan Project. Now that these walls can be more securely dated, a full description is merited. The present study is partly based on the unpublished notes and photographs of Charles Daniels. The walls of Zuwila can now firmly be included among Libya's most important medieval monuments.