Geoffrey de Morton (died c.1317) was a wealthy merchant and shipowner in fourteenth-century Dublin who served as Mayor of Dublin in 1303. He acquired an unsavoury reputation for unscrupulous business methods and corruption, and was responsible for the murage controversy of 1308-1313.
According to Elrington Ball, Geoffrey de Morton came from a prominent Anglo-Norman family which had settled in Dublin, and made his wealth by trading with England, Scotland and France. Presumably his wealth was the main reason he was chosen as Mayor of Dublin, but controversy began almost immediately after his election, when he was accused of stealing the official seal of Dublin Corporation for his own use. Geoffrey insisted that it was not he but his wife Maud who had taken the seal, and the Corporation seem to have accepted this rather implausible explanation, although what possible motive his wife might have had for the theft is unclear.
In 1305 he brought a series of lawsuits against Richard de Beresford, Lord Treasurer of Ireland and the Barons of the Court of Exchequer (Ireland), which failed. The Barons brought a series of counter-claims which were successful, and as a result Geoffrey was briefly imprisoned.
Geoffrey was undeterred by this setback, and in 1308 he applied to King Edward II for a licence to levy a toll for six years to pay for murage, the tax for the upkeep of the Dublin city walls, and of Isolde's Tower, the defensive tower situated at one end of Old Dublin Bridge (now Father Mathew Bridge), which had been damaged by fire. Geoffrey neglected to mention that as the tenant of the tower he was legally obliged to keep it in good repair at his own expense. The licence was granted, but almost at once a flood of complaints about Geoffrey's corrupt management of the tolls began, in particular his practice of exempting his own friends from paying. In addition it appears that none of the money was actually spent on upkeep of the walls, which might have had disastrous consequences during the Bruce campaign in Ireland. Geoffrey also built several houses on the bridge, which it was alleged seriously disrupted the traffic.