PO may stand for:

• Pareto optimality
• Parole Officer
• Per os, Latin for "by mouth" or "orally"
• Perfect Orange a third wave ska based in Knoxville, TN from 2002-2005
• Petty Officer, a Non-Commissioned Officer Rank in many Navies
• Pilkington Optronics, now Thales Optronics
• Pilot Officer, a junior commissioned rank the British and many Commonwealth air forces
• Pissed off (often used as a verb or adjective, as in "POed" or "PO'ed")
• Platforma Obywatelska, a Polish conservative-liberal party
• PO art after POMO post-modernism.(fractals)grafix+nature/myths eg. Ryszard Horowitz, Stan Ostoja-Kotkowski
• Po!, indie band from Leicester
• Pocket Otaku, a character on Atlanta based web forum
• Polar Air Cargo: IATA airline designator
• Portable Object, text translation files used in software localization that are meant to be read and edited by humans
• Portugal: FIPS PUB 10-4 territory code digram
• Post office, as in P.O. Box
• Presiding Officer
• Provocative operation, coined by Edward De Bono and part of a Lateral thinking technique
• Purchase order
• Chemin de Fer de Paris à Orléans, an old railway created to link Paris to Orléans

Po may stand for:

• one of the Teletubbies
• the word for fonio in the Dogon mythology, which states that the whole universe was created out of a grain of po
• A major god in Hawaiian mythology. Ao the male force in the universe, is linked to the sky, day and light; Po, the feminine force, is linked to earth, darkness, and night. see http://www.mythencyclopedia.com/Pa-Pr/Polynesian-Mythology.html
• Petaoctet, a unit of quantity of information
• Po or Poo, a parish of Llanes municipality, in Asturias, Spain
• Pô, a town in Burkina Faso
• Pô (département), part of the Napoleonic Empire
• Pö, a romanization of the Tibetan word བོད་, meaning Tibet
• Po' boy (from "Poor Boy"), a type of submarine sandwich from New Orleans
• Polonium, a chemical element
• Po River, in Italy
• Po River, in the U.S. state of Virginia

po may stand for:

• slang or euphemism for "chamber pot"
• slang usage for "poor", meaning "so poor that you can't afford the o or the r"

PO