Aetius or Aëtius may refer to:
- Aetius (philosopher), 1st- or 2nd-century doxographer and Eclectic philosopher
- Aëtius of Antioch, 4th-century Anomean theologian, called "Aetius the Atheist" by his Trinitarian enemies
- Flavius Aetius, 5th-century Roman general
- Aetius (praetorian prefect), Praetorian prefect of the East in 425
- Aëtius of Amida, 6th-century Byzantine physician
- Sicamus Aëtius, Byzantine medical writer possibly identical with the preceding
- Aetios (eunuch), Byzantine official and general
- Aetius (spider), a spider genus (Corinnidae)