The site was fortified in the 11th century to control the ford across the Gave de Pau. It was built on the north bank, equidistant from Lescar, seat of the bishops, and from Morlaàs, and became the seat of the viscounts of Béarn. Pau was made capital of Béarn in 1464. During the early 16th century, the Château de Pau was made more habitable by Gaston III, count of Foix and became the residence of the kings of Navarre, who were also viscounts of Béarn.
In 1188, Gaston VI assembled his cour majour there, predecessor of the conseil souverain and roughly equivalent to the House of Lords (but predating it). Gaston VII added a third tower in the 13th century. Gaston Fébus (Gaston III of Foix and Gaston X of Béarn) added a brick donjon (keep).
Pau was birthplace of Henry IV of France. His mother, Jeanne d'Albret, crossed into France to ensure her son would be born there. The baby's lips were moistened with the local Jurançon wine and rubbed with garlic shortly after birth. When Henry IV left Pau to become King of France, he remarked to local notables that he was not giving Béarn to France, but giving France to Béarn.
Napoleon III refurbished the château and Pau adding streets of Belle Époque architecture, before the fashion transferred to Biarritz. Pau is still a centre for winter sports and equestrian events, with a steeplechase. King Charles XIV of Sweden, the first royal Bernadotte, was also born in Pau.
Following the assassination of Abraham Lincoln, Mary Todd Lincoln stayed in Pau in the late 1870s, toward the end of her life
