Gormlaith was born at a time when the Norsemen who had been invading and settling Ireland since the eighth century were reaching their full strength against the native kingdoms. In Gaelic Ireland, many areas traditionally had their own separate chieftains, or kings, and Gormlaith’s father, Murchadh, was the hereditary overlord of north Leinster. Marriage alliances between Norse and native were not unusual, and when Gormlaith was a teenager she was married off to the powerful but elderly Olaf Cuarán, king of the Viking town of Dublin. She had five children by Olaf, including her favourite and most ambitious son, Sitric Silkbeard.
Shortly after his marriage, Olaf became high-king of Ireland, or ard rí, by conquest, making Gormlaith his high-queen (ard bean-rí). However, in the year 980 his position was challenged by the young king of Meath, Malachy. The treacherous Gormlaith looked at the young challenger’s chance of success against her old husband – and decided to opt for the winning side. She used her influence in her home province of north Leinster and in her adopted city of Dublin to help Malachy take the high-kingship by force. Malachy then drove Olaf into exile in Scotland and married Gormlaith, making her high-queen for a second time. He also made her half-Viking son, Sitric Silkbeard, king of Dublin in 994.
Meanwhile, in the west of Ireland, Brian Ború, the king of Munster, was becoming ever stronger. Eventually, Malachy was forced to cede territory to him. Gormlaith took this opportunity to change sides once again and persuaded her brother, Mael Mordha, who had by now inherited the kingship of north Leinster, and her son, Sitric, to attack Malachy and take his remaining lands.
This plan backfired when the powerful Brian Ború came to Malachy’s defence, but the tide turned once more in Gormlaith’s favour when Brian Ború realised that the high-kingship was his for the taking. He accepted Gormlaith’s political and sexual advances, made her brother and son his allies, and achieved a position of supremacy over Malachy. After taking the high-kingship from him, Brian married Gormlaith, making her high-queen for the third time, with her third king. Brian Ború’s kingship, which lasted until his death in 1014, is regarded as the first time in history that Ireland came close to being a country united under one native leader.
Twenty years and one child later, Gormlaith was up to her old tricks again. She was manipulating Brian to gain advantages for herself and her family. Tired of her endless wheedling demands, Brian repudiated her. Once again she incited Sitric and Mael Mordha to rise up against the high-king. This resulted in the astute Brian Ború again allying with Gormlaith’s ex-husband, Malachy, and laying siege to Dublin City. He was unconcerned that Gormlaith was in the city at the time.
Sitric gathered together a mighty host, or army, from Norse allies, relations and connections in Britain and Ireland and made war on Brian Ború and Malachy. The decisive moment was the famous Battle of Clontarf, fought on Good Friday 1014, which resulted in a resounding victory for Brian’s forces – and also saw Brian’s death on the battlefield. The Battle of Clontarf ended forever any hopes the Vikings might have had of domination in Ireland. Gormlaith lost her youngest son in the battle. Afterwards she retired to a quiet life and died in a convent in 1042. Her son by Olaf, Sitric Silkbeard, remained king of Dublin for many years.