Archaeological evidence for a Sasanian presence in the 'Uman region of Eastern Arabia is sparse. Recent excavations at the site of Fulayj in Oman have, however, revealed it to be a Late Sasanian fort, the only securely dated example in Arabia, or indeed on the western shores of the Indian Ocean more generally. AMS dating supports the ceramic chronology proposed for the site, demonstrating occupation until the Islamisation of South-eastern Arabia in the early seventh century AD, and also briefly into the very Early Islamic period. Fulayj fort provides new insights into Sasanian military activities during this crucial period of Arabian history.