Massacre of Mullaghmast
1578 CE.
Shown on the map at 53.010°, -6.852°.
The massacre of Mullaghmast (Irish: ár Mhullach maistean) was the mass killing of between 100 and 400 members of the Gaelic nobility of Ireland by English forces under the command of Sir Henry Sidney in Mullaghmast, County Kildare in either late 1577 or 1 January 1578. There is limited surviving documentation on the massacre, although documents have recently been made available at the National Library of Ireland.
Text from the Wikipedia article Massacre of Mullaghmast, licensed CC BY-SA 4.0.