The Battle of Glenn Máma (Irish: Cath Ghleann Máma, The Battle of "The Glen of the Gap") or Glenmama was a battle that took place, most probably near Lyons Hill in Ardclough. County Kildare in AD 999 between Windmill Hill and Blackchurch. It was the decisive and only engagement of the brief Leinster revolt of 999–1000 against the King of Munster, Brian Boru. In it, the combined forces of the Kingdoms of Munster and Meath, under King Brian Boru and the High King of Ireland, Máel Sechnaill II, inflicted a crushing defeat on the allied armies of Leinster and Dublin, led by King Máel Mórda of Leinster.