John I was the name of a number of rulers:

• Pope John I
• King John I of France
• King John I of Castile
• King John I of Scotland
• King John I of Portugal
• King John I of Jerusalem
• King John I of Cyprus
• Emperor John I Tzimisces
• John I, Duke of Bourbon
• John I, Duke of Brabant
• John I, Duke of Brittany
• John I, Duke of Lorraine
• John I, Count of Hainaut
• John I, Count of Holland
• John I, Count of Luxemburg

John of England could also be called John I, but as there has been no second John this is unnecessary, and he is usually referred to simply as "King John". John I was Pope from 523 to 526. ... John I the Posthumous (French: Jean Ier le Posthume) (November 15, 1316 - November 20, 1316) was King of France for the five days he lived. ... John I (August 24, 1358 – 1390) (in Spanish: Juan I) was the king of Castile, was the son of Henry II and of his wife Joan, daughter of John Manuel of Villena, head of a younger branch of the royal house of Castile. ... John Balliol, the son of Devorguilla Balliol and John, 5th Baron de Balliol, was the king of Scotland from November 17, 1292-1296. ... João I, tenth king of Portugal (in English, John I) (the Good or sometimes, the Great or even the One With Good Memory), was born in Lisbon in April 11, 1357 and died in the same city in August 14, 1433. ... John of Brienne (c. ... John II of Jerusalem (died May 20, 1285) was the son of Hugh I of Jerusalem and Isabella of Ibelin. ... Ioannes, protected by God and the Virgin Mary. ... John I of Bourbon (1381 – 1434) was Duke of Bourbon, from 1410 to his death and Duke of Auvergne since 1416. ... Jan I van Brabant, also called John I the Victorious, was born in Brussels in 1253 and died in Louvain on May 3, 1294. ... John I of Dreux (in French Jean I de Dreux) (1217–October 8, 1286), known as the Red due to the colour of his beard, was Duke of Brittany, from 1237 to his death. ... John I (1346 - September 23, 1390) was Duke of Lorraine from 1346 to his death. ... John I of Avesnes (May 1, 1218 - December 24, 1257) was count of Hainaut from 1246 to his death. ... John I (1284-1299) was count of Holland and son of Count Floris V. John inherited the county in 1296 after the murder of his father. ... John the Blind of Luxemburg (August 10, 1296 - August 26, 1346) was King of Bohemia and Count of Luxemburg. ... John (December 24, 1166–October 18/19, 1216) reigned as King of England from April 6, 1199, until his death. ...