Coordinates: 51°28′36.2″N 0°18′42.7″W / 51.476722°N 0.311861°W
Syon Abbey, Sion Abbey or simply Sion was a monastery of the Bridgettine Order founded in 1415 which stood until its demolition in the 16th century on the left (northern) bank of the River Thames within the parish of Isleworth, in the county of Middlesex, on or near the site of the present Georgian mansion of Syon House. It was named after the Biblical Holy “City of David which is Zion” (1 Kings 8:1), built on the eponymous Mount Zion (or Sion, Syon, etc.).
At the time of the dissolution, the abbey was the wealthiest religious house in England. Syon Abbey maintained a substantial library, with a collection for the monks and another for the nuns. When Catherine of Siena's Dialogue of Divine Revelation was translated into English for the abbey, it was given a new title, "The Orchard of Syon," and included a separate prologue written to the nuns.
Syon Abbey was built as part of King Henry V's “The King's Great Work” centred on Sheen Palace (renamed Richmond Palace in 1501). The royal manor of Sheen lay on the right (south), Surrey, bank of the River Thames, opposite the parish of Twickenham and the royal manor of Isleworth on the left, Middlesex, bank. Sheen had been a favourite residence of the last Plantagenet king Richard II (1377–1399) and his beloved wife Anne of Bohemia. When Anne died there of plague in 1394, Richard cursed the place where they had found great happiness and razed the palace to the ground. His throne was usurped by his cousin Henry Bolingbroke, Duke of Lancaster, who ruled as Henry IV (1399–1413), who was involved in the murder of Richard in 1400, and in that of Archbishop Richard le Scrope, and made a vow to expiate his guilt by founding 3 monasteries, which vow he died before fulfilling. The derelict palace was unfavoured by Henry IV but his son Henry V (1413–1422) saw its reconstruction as a means of emphasising the dynastic link between his own House of Lancaster and that of Plantagenet, of unquestioned legitimacy, and decided at the same time to found the 3 monasteries pledged by his father in one great, multi-campus building scheme, known as “The King's Great Work”. Thus the “Great Work” commenced in the winter of 1413-14, comprising a new Sheen Palace, and nearby the following 3 monasteries: