Ambrosius (a Latin adjective derived from the Ancient Greek word ἀμβρόσιος, ambrosios "divine, immortal") may refer to:
- Saint Ambrose (Aurelius Ambrosius), bishop of Milan
- Ambrosius Alexandrinus, a Latinization of the name of Ambrose of Alexandria
- Ambrosius Theodosius Macrobius, Roman grammarian and philosopher
- Ambrosius Ehinger, German conquistador
- Ambrosius Holbein, Swiss painter
- Ambrosius Petruzzy, Italian sculptor
- Ambrosius Bosschaert, Dutch painter
- Ambrosius Brueghel, Dutch baroque painter
- Ambrosius Blarer, Swiss reformer
- Ambrosius Moibanus, German reformer
- Ambrosius Pelargus, German anti-reformer theologian
- Patriarch Ambrose of Georgia, Catholicos Patriarch of All Georgia
- Ambrosius Aurelianus, fifth-century British leader
- Ambrosius, Metropolitan of Moscow
- Ambrosius of Optino
- Ambrosius Stub, poet
- Ambrosius (Hussite), priest, leader of Hussite peasants
- Ambrosius Gudko, Russian bishop
- Ambrosius, a character in the film Labyrinth
- Ambrosius Bogbinder, mayor of Copenhagen 1529–36
- Ambrosios Pleianthidis, Greek Orthodox metropolitan bishop.