Nonius can refer to:
==People==<!--chronological order-->
- Romans belonging to the Nonia gens
- Nonius Marcellus, a Roman grammarian of the 4th or 5th century AD
- Pedro Nunes (Latin: Petrus Nonius) (1502–1578), Portuguese astronomer and mathematician
Other
- Nonius (horse), a breed of horse
- Nonius (device), a precursor to the Vernier scale
- Nonius (crater), a lunar crater
See also
- Nonus
- Nonnus