Diagoras may refer to:
- Diagoras of Melos – an Atheist philosopher and poet (5th century BC)
- Diagoras of Rhodes – a boxer (5th century BC)
- Diagoras – a Greek physician quoted in Natural History of Pliny
- Diagoras F.C. – football club named after Diagoras of Rhodes
- Rhodes International Airport, "Diagoras"
- Mr Diagoras, a character from the British science fiction series Doctor Who who became the human part of Dalek Sec, a Dalek-human hybrid
- Doctor Diagoras, one of the mad scientists of Stanisław Lem
- Diagoras ephialtes - a species of stick insect in the subfamily Platycraninae