Simon I de Senlis, Earl of Huntingdon-Northampton

Simon I de Senlis (or Senliz, St. Liz, etc.), 1st Earl of Northampton and 2nd Earl of Huntingdon jure uxoris (died between 1111 and 1113; most likely 1111 as this is when his castle at Northampton passed to the crown) was a Norman nobleman.

In around 1096, Simon de Senlis joined the First Crusade to the Holy Land. There he would have seen the Church of the Holy Sepulchre near the centre of Jerusalem, which he later copied when building one of the four remaining round churches in England, The Holy Sepulchre, Northampton.

In 1098 he was captured during the Vexin campaign of King William Rufus and was subsequently ransomed. He witnessed King Henry I’s Charter of Liberties issued at his coronation in 1100. He attested royal charters in England from 1100 to 1103, 1106 to 1107, and 1109 to 1111. Sometime in the period 1093–1100, he and his wife, Maud, founded the Priory of St Andrew's, Northampton. He witnessed a grant of King Henry I to Bath Abbey on 8 August 1111 at Bishop's Waltham, as the king was crossing to Normandy.

As well as The Holy Sepulchre church in Northampton, he built Northampton Castle and the town walls.^[1]

Simon de Senlis subsequently went abroad and died at La Charité-sur-Loire, where he was buried in the new priory church. The date of his death is uncertain.