Pio can refer to:
- Pio Laghi (1922-2009), Italian RC Cardinal
- Pio of Pietrelcina (popularly known as Padre Pio), the stigmatic Capuchin friar, Roman Catholic saint
- Pio Terei, New Zealand actor, singer and comedian
- Pope Pius, the name borne by twelve Roman Catholic pontiffs (the Italian form of Pius is "Pio")
- Pio, abbreviation of Pebioctet, a unit of information or computer storage
- Pio Island, Solomon Islands
The acronym PIO can refer to:
- Programmed input/output, a transfer method for IDE harddisks and network cards
- Peripheral Input/Output, an I/O circuit
- Public information officer of a government department
- Person of Indian Origin, an overseas/expatriate Indian who has certain rights of citizenship
- Pilot-induced oscillation
- Police Intelligence Operations, one of the five functions of the U.S. Army Military Police
- Peruvian Inca Orchid, a breed of hairless dog originating in Peru