| Ordino | 0 | Andorra | AD-05 |
| ORE | 0 | Russia | RU-ORE |
| Örebro County | 0 | Sweden | SE-T |
| ORK | 0 | United Kingdom | GB-ORK |
| ORL | 0 | Russia | RU-ORL |
| Ormož Municipality | 0 | Slovenia | SI-087 |
| Osijek-Baranja County | 0 | Croatia | HR-14 |
| Osilnica Municipality | 0 | Slovenia | SI-088 |
| Oslo | 0 | Norway | NO-03 |
| Oslomej Municipality | 0 | Republic of North Macedonia | MK-57 |
| Östergötland County | 0 | Sweden | SE-E |
| Østfold | 0 | Norway | NO-01 |
| Ostrava-město | 0 | Czech Republic | CZ-806 |
| Ostrobothnia | 0 | Finland | FI-12 |
| OT | 0 | Romania | RO-OT |
| Oulu Province | 0 | Finland | FI-OL |
| OV | 0 | Netherlands | NL-OV |
| OW | 0 | Switzerland | CH-OW |
| OXF | 0 | United Kingdom | GB-OXF |
| OY | 0 | Ireland | IE-OY |
| Ozolnieki Municipality | 0 | Latvia | LV-069 |
| P | 0 | Spain | ES-P |
| PA | 6 | United States | US-PA |
| Pagėgiai municipality | 0 | Lithuania | LT-29 |
| Päijänne Tavastia | 0 | Finland | FI-16 |
| Pakruojis District Municipality | 0 | Lithuania | LT-30 |
| Palanga City Municipality | 0 | Lithuania | LT-31 |
| Panevėžys City Municipality | 0 | Lithuania | LT-32 |
| Panevėžys County | 0 | Lithuania | LT-PN |
| Panevėžys District Municipality | 0 | Lithuania | LT-33 |
| Paola | 0 | Malta | MT-39 |
| Pardubice | 0 | Czech Republic | CZ-532 |
| Pardubický kraj | 0 | Czech Republic | CZ-53 |
| Pārgauja Municipality | 0 | Latvia | LV-070 |
| Paris | 0 | France | FR-75 |
| Pärnu County | 0 | Estonia | EE-67 |
| Pasvalys District Municipality | 0 | Lithuania | LT-34 |
| Pāvilosta Municipality | 0 | Latvia | LV-071 |
| Pays de la Loire | 0 | France | FR-PDL |
| Pazardzhik Province | 0 | Bulgaria | BG-13 |
| Pčinja District | 0 | Serbia | RS-24 |
| PD | 0 | Poland | PL-PD |
| PE | 15 | Canada | CA-PE |
| PE | 0 | Hungary | HU-PE |
| Pehčevo Municipality | 0 | Republic of North Macedonia | MK-60 |
| Pelhřimov | 0 | Czech Republic | CZ-633 |
| Pella Regional Unit | 0 | Greece | GR-59 |
| Peloponnese Region | 0 | Greece | GR-J |
| PEM | 0 | United Kingdom | GB-PEM |
| Pembroke | 0 | Malta | MT-40 |
| Peqin District | 0 | Albania | AL-PQ |
| PER | 0 | Russia | RU-PER |
| Përmet District | 0 | Albania | AL-PR |
| Pernik Province | 0 | Bulgaria | BG-14 |
| Pesaro and Urbino Province | 0 | Italy | IT-PU |
| Pesnica Municipality | 0 | Slovenia | SI-089 |
| Petnjica Municipality | 0 | Montenegro | ME-23 |
| Petrovec Municipality | 0 | Republic of North Macedonia | MK-59 |
| PH | 0 | Romania | RO-PH |
| Phthiotis Prefecture | 0 | Greece | GR-06 |
| Picardy | 0 | France | FR-S |
| Piedmont | 0 | Italy | IT-21 |
| Pietà | 0 | Malta | MT-41 |
| Piran Municipality | 0 | Slovenia | SI-090 |
| Pirkanmaa | 0 | Finland | FI-11 |
| Pirot District | 0 | Serbia | RS-22 |
| Písek | 0 | Czech Republic | CZ-314 |
| Pivka Municipality | 0 | Slovenia | SI-091 |
| PK | 0 | Poland | PL-PK |
| PKN | 0 | United Kingdom | GB-PKN |
| Planken | 0 | Liechtenstein | LI-05 |
| Plasnica Municipality | 0 | Republic of North Macedonia | MK-61 |
| Plav Municipality | 0 | Montenegro | ME-13 |
| Pļaviņas Municipality | 0 | Latvia | LV-072 |
| Pleven Province | 0 | Bulgaria | BG-15 |
| Pljevlja Municipality | 0 | Montenegro | ME-14 |
| Plovdiv Province | 0 | Bulgaria | BG-16 |
| Plungė District Municipality | 0 | Lithuania | LT-35 |
| Plužine Municipality | 0 | Montenegro | ME-15 |
| PLY | 0 | United Kingdom | GB-PLY |
| Plzeň-jih | 0 | Czech Republic | CZ-324 |
| Plzeň-město | 0 | Czech Republic | CZ-323 |
| Plzeň-sever | 0 | Czech Republic | CZ-325 |
| Plzeňský kraj | 0 | Czech Republic | CZ-32 |
| PM | 0 | Spain | ES-PM |
| PM | 0 | Poland | PL-PM |
| PNZ | 0 | Russia | RU-PNZ |
| Podčetrtek Municipality | 0 | Slovenia | SI-092 |
| Podgorica Municipality | 0 | Montenegro | ME-16 |
| Podlehnik Municipality | 0 | Slovenia | SI-172 |
| Podunavlje District | 0 | Serbia | RS-10 |
| Podvelka Municipality | 0 | Slovenia | SI-093 |
| Pogradec District | 0 | Albania | AL-PG |
| Poitou-Charentes | 0 | France | FR-T |
| POL | 0 | United Kingdom | GB-POL |
| Poljčane Municipality | 0 | Slovenia | SI-200 |
| Põlva County | 0 | Estonia | EE-65 |
| Polzela Municipality | 0 | Slovenia | SI-173 |
| Pomoravlje District | 0 | Serbia | RS-13 |
| POR | 0 | United Kingdom | GB-POR |
