Apollonius may be:
- Historical people
- Apollonius Cronus (fl. 4th century BC), philosopher of the Megarian school
- Apollonius of Rhodes (born c. 270 BC), librarian and poet
- Apollonius of Aphrodisias (3rd century BC?), historian of Caria (FGrHist no. 740)
- Apollonius of Perga (262–190 BC), geometer and astronomer
- Apollonius of Tralles (fl. 2nd century BC), sculptor
- Apollonius paradoxographus (2nd century BC), paradoxographer
- Apollonius (physician), several physicians in Ancient Greece and Rome
- Apollonius the Effeminate (fl. 120 BC) a Greek rhetorician of Alabanda in Caria
- Apollonius Molon (fl. 70 BC), rhetorician
- Apollonius of Tyre (philosopher) (fl. 60 BC), Stoic philosopher
- Apollonius of Athens (fl. 1st century BC), sculptor
- Apollonius of Citium (fl. 1st century BC), physician
- Apollonius the Sophist of Alexandria, a famous grammarian who probably lived towards the end of the 1st century AD
- Apollonius of Tyana (ca. 40—120 AD), Pythagorean philosopher
- Apollonius Dyscolus (fl. 2nd century AD), grammarian
- Apollonius the Apologist (died c. 186 AD), religious leader
- Apollonius of Ephesus (fl. 180-210 AD), religious leader and writer
- Apollonius (praetorian prefect) (442-443), Roman Praetorian prefect
- Apollonius (magister militum) (fl. 443-451), Eastern Roman general
- Apollonius (consul 460), consul in 460
- Other
- Apollonius of Tyre, medieval fictional character
- Apollonius (crater), on moon
- Apollonius' theorem, an elementary geometry theorem about triangles
- Circles of Apollonius