Regio (pl. regiones) is the Latin word for ‘region’ and the Italian word for ‘royal’

It may refer to:

• Regiopolis, a concept for urban centers in between metropolitan areas.

Ancient toponymy

• Regiones of Augustan Italy, the departments in which Roman Emperor Augustus divided Italy.
• 14 regions of the Augustan Rome, in ancient Rome as a name for quartiers of the city of Rome
• 14 regions of Medieval Rome, resulting from the redivision of the Rome after the revolution of 1143
• Regio, in ancient Constantinople as a name for the 14 quarters of the city of Constantinople, defined in analogy with those of Rome
• Regio Aromatica, name for the Horn of Africa
• Regiones, administrative subdivisions of the kingdoms of Anglo-Saxon England

Astronomy

• Regio (astronomy), which, in planetary geology, is a large area of a planet or moon that is strongly differentiated in colour or albedo
  • A regio of Venus:
    • Alpha Regio
    • Asteria Regio
    • Beta Regio
    • Ovda Regio
  • A regio of Pluto:
    • Belton Regio
    • Lowell Regio
    • Tombaugh Regio
  • A regio of Titan:
    • Tui Regio
  • A regio of Ganymede:
    • Galileo Regio
  • A regio on Phoebe:
    • Leto Regio
  • A regio on Iapetus:
    • Cassini Regio