Christian I generally refers to Christian I of Denmark. It may also refer to:
Christian I (Archbishop of Mainz) (c. 1130–1183) Christian I, Count of Oldenburg (died 1167) Christian I, Elector of Saxony (1560–1591) Christian I, Prince of Anhalt-Bernburg (1568–1630) Christian I, Count Palatine of Birkenfeld-Bischweiler (1598–1654) Christian I, Duke of Saxe-Merseburg (1615–1691) Christian Adolf I, Duke of Schleswig-Holstein-Sonderburg-Franzhagen (1641–1702) Christian August I, Duke of Schleswig-Holstein-Sonderburg-Augustenburg (1696–1754) Christian Günther I, Count of Schwarzburg-Sondershausen (1578–1642) Christian Louis I, Duke of Mecklenburg (1623–1692) Christian Ulrich I, Duke of Württemberg-Oels (1652–1704)