Syon Abbey, (or Sion Abbey) was a major medieval monastery of the Bridgettine Order in the late Gothic or Perpendicular style (with alterations to meet the needs of this very distinctive order), its major site bordering Brentford and Isleworth, Middlesex, England. Syon House, seat of the Duke of Northumberland, partly overlies the site, which was identified as lying between Syon House and the River Thames. The abbey's remains were partially uncovered in excavations starting in 2003.