The Treaty of Wallingford of 1153, aka Treaty of Winchester or as the Treaty of Westminster, was an agreement that effectively ended the civil war known as the Anarchy, caused by a dispute between Empress Matilda and her cousin King Stephen of England over the English crown. The Treaty of Wallingford forced Stephen to recognise Matilda's son Henry of Anjou, who became Henry II, as his heir, while Stephen kept the throne until he died.
Stephen had built countercastles near Wallingford to attack Matilda’s supporter Brien FitzCount at Wallingford Castle. Henry launched attacks on those countercastles, and a battle between the forces was expected. However William d'Aubigny, 1st Earl of Arundel successfully argued the futility of further fighting. A temporary truce was reached at Wallingford on the banks of the Thames, but Stephen's son Eustace opposed settling. However, after Eustace's sudden death in August 1153, it appears that a more formal agreement was written at Winchester in November 1153, signed later at Westminster. The agreement called for the dismantling of Stephen's countercastles.
Henry II later rewarded Wallingford for its assistance in the struggle by giving the town its royal charter in 1155.