Saint Alexander may refer to one of several saints including:
- Pope Alexander I (died 115), saint and pope
- See Epipodius and Alexander for Saint Alexander, martyred in Lyon, 178 AD
- Alexander of Rome (died c. 289), Christian martyr
- Alexander of Bergamo (died c. 303), patron saint of Bergamo; may have been a Roman soldier
- Alexander of Constantinople (born between 237 and 244–337), bishop of Byzantium and the bishop of Constantinople
- Alexander of Jerusalem (d. 251 AD), venerated as a Martyr and Saint by Eastern Orthodox Churches & Roman Catholic Church
- Alexander Nevsky (1220–1263), Grand Prince of Novgorod and Vladimir
- Alexander Sauli, the "Apostle of Corsica", (1535–1592), member of an illustrious Lombard family
- Alexander of Comana (died 251), bishop of Comana
- Pope Alexander I of Alexandria, Patriarch of Alexandria
- Alexander Svirsky (1448–1533), Eastern Orthodox saint, monk and hegumen of Russian Orthodox Church
- One of the seven sons of Felicitas of Rome (101–165)
- Sisinnius, Martyrius and Alexander (died 405), martyrs
- Saint Alexander, a companion of St. Victor of Marseilles (died 290)
- Alexander Schmorell (1917–1943), member of the White Rose