|Birth||January 1, 1250|
|Death||June 12, 1294 (Clermont, canton of Clermont, arrondissement of Clermont, Oise)|
John I of Brienne (died 12 June 1294) was the son of Alphonso of Brienne and Marie de Lusigan. His mother was the heiress of Eu, Seine-Maritime, and he succeeded his father as Count of Eu in 1270.
He married Beatrice, the daughter of Guy III, Count of Saint-Pol. They had five children:
- John II of Brienne, Count of Eu
- Isabelle (d. 1302/07), married John II of Dampierre, Viscount of Troyes (d. c.1307)
- Jeanne (d. aft. 12 March 1325), married first Raymond VI, Viscount of Turenne (d. 1304), married second before 4 August 1314 Renauld, Lord of Picquigny, vidame of Amiens (d. 1315)
- Marguerite (d. 1310), married Guy, Viscount of Thouars (d. 1308)
- Mahaut (d. aft. 1328), married Alfonso de la Cerda
John died at Clermont-en-Beauvaisis in 1294.