Attalus may refer to:
- Several members of the Attalid dynasty of Pergamon
- Attalus I, ruled 241 BC–197 BC
- Attalus II Philadelphus, ruled 160 BC–138 BC
- Attalus III, ruled 138 BC–133 BC
- Attalus (general), courtier and general of Philip II of Macedonia
- Attalus (son of Andromenes), general of Alexander the Great and Perdiccas
- Attalus of Rhodes, (2nd century BC), astronomer, contemporary of Hipparchus
- Attalus (Stoic), Stoic philosopher (c. 25 AD) and teacher of Seneca
- Priscus Attalus, Roman senator who was proclaimed emperor twice by the Visigoths
- Attalus (beetle), a genus of beetles in the Malachiidae family