| Piraeus | |
| Native Name: | Νομός Πειραιά |
| Settlement Type: | Former prefecture |
| Image Map1: | Pireas nomarchia municipalities numbered.png |
| Map Caption1: | Location of municipalities within Piraeus Prefecture |
| Subdivision Type: | Country |
| Subdivision Name: | Greece |
| Subdivision Type1: | Periphery |
| Parts Type: | Subdivisions |
| P1: | 5 provinces |
| P2: | 16 municipalities |
| P3: | 2 communities |
| Established Title: | Established |
| Established Date: | 1972 |
| Extinct Title: | Disestablished |
| Extinct Date: | 2010 |
| Seat Type: | Capital |
| Seat: | Piraeus |
| Unit Pref: | Metric |
| Area Total Km2: | 929 |
| Area Rank: | 47th |
| Population Total: | 541504 |
| Population As Of: | 2001 |
| Population Density Km2: | auto |
| Population Density Rank: | 2nd |
| Population Rank: | 3rd |
| Postal Code Type: | Postal codes |
| Postal Code: | 1xx xx, 801 xx |
| Area Code Type: | Area codes |
| Area Code: | 21x, 2736 |
| Iso Code: | GR-A4 |
| Registration Plate: | ΥΝ |
| Website: | nomarhiapeiraia.gr |
Piraeus Prefecture (el|Νομός Πειραιά or Νομός Πειραιώς) was one of the prefectures of Greece. Created in 1964 as a separate Prefecture (Νομός) and after the dissolution of the prefecture in 1972 was one of the 4 prefectures (Νομαρχίες) of Attica prefecture, and from 1994, part of the Athens-Piraeus super-prefecture (1994–2011). The capital of the prefecture was Piraeus. As a part of the 2011 Kallikratis government reform, the prefecture was abolished, and its territory was divided into two regional units: Islands and Piraeus.
The prefecture covered the south-western part of the agglomeration of Athens, several islands in the Saronic Gulf (Salamis, Aegina, Agkistri, Poros, Hydra, Dokos, Spetses, Spetsopoula), Methana and Troizina on the Peloponnese peninsula, and the islands of Kythira and Antikythera south of the Peloponnese. An indication of the geographical diversity of the prefecture was the stark difference in population density between its seven mainland municipalities in the Athens urban area, which have 9,244.2 inhabitants/km2, and its detached outlying areas, which average only 85.83 inhabitants/km2 (and most of these on Salamis Island, at 395.40/km2, while the far-outlying parts have only 47.80/km2).
| Municipality |
| Greek name | Seat (if different) | YPES code |
|---|---|---|---|---|
| 3 | Αίγινα | 4003 | ||
| 2 | Άγιος Ιωάννης Ρέντη | 4001 | ||
| 17 | Αγκίστρι | Megalochóri | 4002 | |
| 4 | Αμπελάκια | 4004 | ||
| 18 | Αντικύθηρα | Potamós | 4005 | |
| 5 | Δραπετσώνα | 4006 | ||
| 16 | Ύδρα | 4018 | ||
| 6 | Κερατσίνι | 4007 | ||
| 7 | Κορυδαλλός | 4008 | ||
| 8 | Κύθηρα | 4009 | ||
| 9 | Μέθανα | 4010 | ||
| 10 | Νίκαια | 4011 | ||
| 11 | Πέραμα | 4013 | ||
| 1 | Πειραιάς | 4012 | ||
| 12 | Πόρος | 4014 | ||
| 13 | Σαλαμίνα | 4015 | ||
| 14 | Σπέτσες | 4016 | ||
| 15 | Τροιζήνα | 4017 | ||
Note: Provinces no longer hold any legal status in Greece.
See also: List of settlements in Attica.