Battle of Islandbridge: High King Niall Glúndub is killed while leading an Irish coalition against the Vikings of Uí Ímair, led by King Sitric Cáech.

The Battle of Islandbridge, also called the Battle of Áth Cliath, took place on 14 September 919, between a coalition of native Irish, led by Niall Glúndub, overking of the Northern Uí Néill and High King of Ireland, and the Dublin-based Vikings of the Uí Ímair, led by Sitric Cáech. It was one in a series of battles initiated by the native Irish to attempt to drive the Vikings of the Uí Ímair from Ireland. The battle was a decisive victory for Sitric Cáech and the Uí Ímair, with Niall Glúndub and five other Irish kings dying in the battle.

September 14 is the 257th day of the year in the Gregorian calendar; 108 days remain until the end of the year.