Simon I de Senlis, Earl of Huntingdon-Northampton

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

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 1100–03, 1106–07, and 1109–011. 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. 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.

He built Northampton Castle, the town walls and one of the three remaining round churches in England, The Holy Sepulchre, Northampton.

Simon was the third son of Laudri de Senlis, sire of Chantilly and Ermenonville (in Picardy), and his spouse, Ermengarde.

He married in or before 1090 Maud of Huntingdon, daughter of Waltheof, Earl of Northumbria, Northampton, and Huntingdon, by Judith, daughter of Lambert, Count of Lens. They had two sons, Simon II de Senlis, Earl of Huntingdon-Northampton, and Waltheof of Melrose, and one daughter, Maud de Senlis, who married (1st) Robert Fitz Richard (of the De Clare family), of Little Dunmow, Essex.

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