John Casimir
John Casimir may refer to:
- John Casimir (clarinetist)
- John Casimir of the Palatinate-Simmern, Count Palatine of Lautern from 1576
- John Casimir, Count of Erbach-Breuberg
- John Casimir, Count Palatine of Kleeburg, father of Karl X Gustav of Sweden
- John Casimir, Duke of Saxe-Coburg
- John Casimir, Prince of Anhalt-Dessau, German prince of the House of Ascania
- John Casimir of Poland