Modius (plural modii) may refer to:

  • an ancient Roman unit for dry measures, (8.73 L) roughly equivalent to a peck
  • a medieval Roman unit for area, approximately 40 acres
  • Modius (headdress), a type of cylindrical headdress so called for its resemblance to the measure of grain
  • Modius, the family name of the Modia (gens)
  • Modius (beetle), a genus in the family Eucnemidae

See also