John I of Opava-Ratibor (; ; c. 1322 â 1380 or 1382 ) was the founder the Opava branch of the Bohemian Pà Âemyslid dynasty, which lasted until 1521. In 1365, he became the sole heir of the Duchy of Racibórz. From 1367 to 1377 he ruled the Duchy of Opava () jointly with his brothers, Nicholas III, Wenceslaus I and Przemko I. From 1377 until his death, he was also Duke of Krnov and Bruntál.
His parents were Nicholas II of Opava and Anna of Racibórz, a sister of Leszek of Racibórz, the last Duke of Racibórz from the Silesian Piast family. Leszek died in 1336 without heirs, causing Ratiboà  to revert to the Crown. King John of Bohemia then enfeoffed Leszek's brother-in-law, Nicholas II, who was John I's father. Since John I was the only son of Nicholas II from his first marriage with Anna, John I was the sole heir of Racibórz. At the same time, he and his younger half-brother Nicholas III became guardians of Nicholas III's younger brothers Wenceslaus I and Pà Âemysl. After disputes about the inheritance, Opava was divided in 1367 among the four brothers. In 1377, a new division was made, in which John I kept Racibórz, but also received the duchies of Krnov and Bruntál. The Duchy of Gà Âubczyce was split off for Nicholas III; Wenceslaus I and Pà Âemysl received the rest of Opava. When Wenceslaus died in 1381, Pà Âemysl inherited Wenceslaus's share. When Nicholas III died in 1394, Pà Âemysl inherited Gà Âubczyce as well.
John I gave Magdeburg rights to the city of Opava in 1372. Because of financial difficulties, he sold Mikoà Âów and the Principality of Pless to Duke Wà Âadysà Âaw II of Opole in 1375. His son John II later managed to buy both these possession back.
In 1361 John I married to Anna, daughter of Henry V the Iron, Duke of à »agaà  and Gà Âogów (d. 1369). They had three children