William I of Scotland, also known as William the Lion, reigned from 1165 to 1214. He was the son of Henry, Earl of Northumbria and Ada de Warenne. His reign was marked by efforts to strengthen the Scottish monarchy and expand its territories, particularly through military campaigns against the English. William's rule faced challenges, including conflicts with King Henry II of England. In 1174, he was captured during a battle and subsequently forced to sign the Treaty of Falaise, which recognized English overlordship over Scotland. Despite this setback, he worked to restore Scotland's independence after his release in 1189.