Administrative regions of Greece in the context of "Regional units of Greece"

Attica (/ˈætɪkə/ AT-ih-kə; Greek: Περιφέρεια Αττικής, romanized: Periféria Attikís, [periˈferi.a atiˈcis]) is an administrative region of Greece that encompasses the entire Athens metropolitan area, the core city of which is the country's capital and largest city, Athens. The region is coextensive with the former Attica Prefecture of Central Greece and covers a greater area than the historical region of Attica.

Thessaloniki (/ˌθɛsələˈniːki/; Greek: Θεσσαλονίκη [θesaloˈnici] ; also known by various spellings and names) is a city in northern Greece. The nation's second-largest, with slightly over one million inhabitants in its metropolitan area, it is the capital of the geographic region of Macedonia, the administrative region of Central Macedonia and the Decentralized Administration of Macedonia and Thrace. It is also known in Greek as i Symprotévousa, literally "the co-capital", a reference to its historical status as the "co-reigning" city (Symvasilévousa) of the Byzantine Empire alongside Constantinople.

Thessaloniki is located on the Thermaic Gulf, at the northwest corner of the Aegean Sea. It is bounded on the west by the delta of the Axios. The municipality of Thessaloniki, the historical centre, had a population of 319,045 in 2021, while the Thessaloniki metropolitan area had 1,006,112 inhabitants and the greater region had 1,092,919. It is Greece's second major economic, industrial, commercial and political centre, and a major transportation hub for Greece and southeastern Europe, notably through the Port of Thessaloniki. The city is renowned for its festivals, events and vibrant cultural life in general. Events such as the Thessaloniki International Fair and the Thessaloniki International Film Festival are held annually. Thessaloniki was the 2014 European Youth Capital. The city's main university, Aristotle University, is the largest in Greece and the Balkans.

The Decentralized Administration of Macedonia and Thrace (Greek: Αποκεντρωμένη Διοίκηση Μακεδονίας–Θράκης) is one of the seven decentralized administrations of Greece, consisting of the peripheries of Central Macedonia and Eastern Macedonia and Thrace. The region is centered in the metropolitan city of Thessaloniki in Central Macedonia.

The Aegean Islands are the group of islands in the Aegean Sea, with mainland Greece to the west and north and Turkey to the east; the island of Crete delimits the sea to the south, those of Rhodes, Karpathos and Kasos to the southeast. The ancient Greek name of the Aegean Sea, Archipelago (ἀρχιπέλαγος, archipelagos), was later applied to the islands it contains and is now used more generally, to refer to any island group.

The vast majority of the Aegean Islands belong to Greece, being split among nine administrative regions. The only sizable possessions of Turkey in the Aegean Sea are Imbros (Gökçeada) and Tenedos (Bozcaada), in the northeastern part of the sea. Various smaller islets off Turkey's western coast are also under Turkish sovereignty.

Rhodes (/roʊdz/ ; Greek: Ρόδος, romanized: Ródos [ˈroðos]) is the largest of Greece's Dodecanese islands and their historical capital; it is the ninth largest island in the Mediterranean Sea. Administratively, Rhodes constitutes a separate municipality within the Rhodes regional unit, which is part of the South Aegean administrative region. The principal town of the island and seat of the municipality is the city of Rhodes, home to its 50,636 inhabitants according to its 2011 census. By 2022, the island’s population had grown to 125,113 people. Located northeast of Crete and southeast of Athens, Rhodes is often referred to by several nicknames: the "Island of the Sun" after its patron sun god Helios; "The Pearl Island"; and "The Island of the Knights", a reference to the Knights of Saint John of Jerusalem, who ruled the island from 1310 to 1522.

Historically, Rhodes was famous for the Colossus of Rhodes, one of the Seven Wonders of the Ancient World. The Medieval Old Town of the City of Rhodes has been declared a World Heritage Site. During the early 21st century the island was one of the most popular tourist destinations in Europe.

Kos or Cos (/kɒs, kɔːs/; Greek: Κως [kos]) is a Greek island, which is part of the Dodecanese island chain in the southeastern Aegean Sea. Kos is the third largest island of the Dodecanese, after Rhodes and Karpathos; it has a population of 37,089 (2021 census), making it the second most populous of the Dodecanese after Rhodes. The island measures 42.1 by 11.5 kilometres (26 by 7 miles). Administratively, Kos constitutes a municipality within the Kos regional unit, which is part of the South Aegean region. The principal town of the island and seat of the municipality is the town of Kos.

Following the implementation on 1 September 2019 of the Kleisthenis I Programme, the administrative divisions of Greece consist of two main levels: the regions and the municipalities. In addition, a number of decentralized administrations overseeing the regions exist as part of the Ministry of the Interior, but are not part of local government. The old prefectures were either abolished and divided or transformed into regional units in 2011 by Kallikratis Plan. The administrative regions are divided into regional units which are further subdivided into municipalities. The Eastern Orthodox monastic community on Mount Athos is an autonomous self-governing entity.

The decentralized administrations (Greek: αποκεντρωμένες διοικήσεις, romanized: apokentroménes dioikíseis) is a tier of the Greek public administration of Greece. They are not elected governing bodies, but are appointed by the national government to supervise the regions and municipalities within their territory. They were created in January 2011 as part of a far-reaching reform of the country's administrative structure, the Kallikratis reform (Law 3852/2010).

They are run by a government-appointed general secretary, assisted by an advisory council drawn from the regional governors and the representatives of the municipalities. They enjoy both administrative and financial autonomy and exercise devolved state powers in urban planning, environmental and energy policy, forestry, migration and citizenship. Beyond that, they are tasked with supervising the first and second-level self-governing bodies, the regions and municipalities.