| Honorific-Prefix: | Sir |
| William Joynier | |
| Office: | Mayor of London |
| Term Start: | 1239 |
| Term End: | 1240 |
| Predecessor: | Richard Renger |
| Successor: | Gerard Bat |
| Occupation: | Merchant, Banker |
| Office1: | Sheriff of the City of London and Middlesex |
| Termstart2: | 1222 |
| Termend2: | 1223 |
| Predecessor2: | Thomas Lambert |
| Successor2: | John Travers |
Sir William Joynier was a rich 13th-century merchant and Sheriff of the City of London who served as Mayor of London from 1239 to 1240.
In 1204 Joynier was instructed to investigate the condition of Newgate Prison and Holborn Bridge and authorise repairs. He was able to make loans to Henry III from a young age. From 1219 Joynier supplied the royal household with luxury goods and built an extensive trading network that extended from Scotland and Ireland to Poitou.[1]
Joynier was made Sheriff of the City of London in 1223.[2] He was subsequently elected to serve as 12th Mayor of London between 1239 and 1240.[3]
Joynier's relationship with the monarch was not always an easy one. The fine rolls of Henry III for 1224 contain an order for Joynier's arrest in order to recover possessions given to Joynier by the disgraced Falkes de Breauté.[4] Joynier had a more serious conflict with Henry in 1239 when, whilst serving as Mayor, he defended the city's privileges and refused to admit Simon FitzMary, appointed by the king without election. However, these incidents did not deter Joynier's trade with the royal household or relationship with the court. Joynier supplied wine to the king in 1241 and was appointed as one of the custodians of the royal treasure in the Tower of London in 1242.[1]
Apart from banking and trade, Joynier also had income from estates in Middlesex and Cambridgeshire. He also had a number of tenements in the city in Cheapside, All Hallows Honey Lane and St. Mary Magdalen, Milk Street[1]
Joynier used some of his wealth to pay for the entire construction of the Greyfriars chapel and contributed two hundred pounds towards construction of other monastic buildings on the site in Saint Nicholas in the Shambles.[5] Joynier's support for the Friars spanned the latter two decades of his life.
Joynier died in about 1248.[1]