Peter I
Peter I may refer to:
Religious hierarchs
- Saint Peter, a.k.a. Simon Peter, Simeon, or Simon, apostle of Jesus
- Pope Peter I of Alexandria, revered as a saint
- Peter I of Armenia, Catholicos of the Armenian Apostolic Church
- Peter I
- Peter I , a Benedictine monk
Rulers
- Peter I of Bulgaria, emperor of Bulgaria
- Peter I of Savoy, count of Savoy
- Peter I of Aragon and Navarre, King of Aragon and Pamplona
- Peter I of Barcelona, Peter II the Catholic, King of Aragon, Count of Barcelona
- Peter I of Constantinople, emperor, Peter II of Courtenay
- Peter I, Duke of Brittany, Peter Mauclerc
- Peter I, Count of Urgell, second son of King Sancho I of Portugal
- Peter I of Valencia, Peter the Great, Peter III of Aragon, king
- Peter I, Duke of Bourbon, second Duke of Bourbon
- Peter I of Portugal, king of Portugal, Peter the Just, Peter the Cruel
- Peter I of Cyprus, Pierre I de Lusignan, king of Cyprus and titular King of Jerusalem
- Peter of Castile, king of Castile and León, Peter the Just, Peter the Cruel
- Petru I of Moldavia, prince of Moldavia 1367–1368
- Peter I, Count of Saint-Pol, Peter of Luxembourg
- Pedro I of Kongo, Pedro I Nkanga a Mvemba
- Peter the Great, Peter I, first Russian czar titled emperor
- Peter I of the Miskito nation, ruled 1729–1739
- Peter I of Montenegro, Petar I Petrović-Njegoš, legate of Serbian Orthodox Church
- Peter I, Grand Duke of Oldenburg, Peter Frederick Louis of Holstein-Gottorp
- Pedro I of Brazil, founder and first ruler of the Empire of Brazil
- Peter I of Serbia, the last King of Serbia