Administrative divisions of Greece in the context of "Prefectures of Greece"

The traditional geographic regions of Greece (Greek: γεωγραφικά διαμερίσματα, lit. 'geographic departments') are the country's main historical-geographic regions, and were also official administrative regional subdivisions of Greece until the 1987 administrative reform. Despite their replacement as first-level administrative units by only partly identical administrative regions (Greek: περιφέρειες), the nine traditional geographic regions—six on the mainland and three island groups—are still widely referred to in unofficial contexts and in daily discourse.

As of 2011, the official administrative divisions of Greece consist of 13 regions (Greek: περιφέρειες)—nine on the mainland and four island groups—which are further subdivided into 74 regional units and 325 municipalities. Formerly, there were also 54 prefectures or prefectural-level administrations.

The regions of Greece (Greek: περιφέρειες, romanized: periféreies) are the country's thirteen second-level administrative entities, counting decentralized administrations of Greece as first-level. Regions are divided into regional units, known as prefectures until 2011.

The 74 regional units of Greece are the country's third-level administrative units (counting decentralized administrations as first-level). They are subdivisions of the country's 13 regions, and are further divided into municipalities.

They were introduced as part of the Kallikratis administrative reform on 1 January 2011 and are comparable in area and, on the mainland, coterminous with the "pre-Kallikratis" prefectures of Greece.

Kleisthenis I Programme (Greek: Πρόγραμμα Κλεισθένης Ι, romanized: Prógramma Kleisthénis I) is the common name of Greek law 4555/2018 of July 2018, a major administrative reform in Greece. It brought about the third major reform of the country's administrative divisions following the 1997 Kapodistrias reform and the 2010 Kallikratis Programme. Named after ancient Greek legislator Cleisthenes, the programme was adopted by the Hellenic Parliament in July 2018 and implemented in September 2019.

The goal of the Kleisthenis I Programme was to reform the election procedures and to strengthen the competences of the local administrative units. The main changes were:

The Kallikratis Programme (Greek: Πρόγραμμα Καλλικράτης, romanized: Prógramma Kallikrátis) is the common name of Greek law 3852/2010 of 2010, a major administrative reform in Greece. It brought about the second major reform of the country's administrative divisions following the 1997 Kapodistrias reform.

Named after ancient Greek architect Callicrates, the programme was presented by the socialist Papandreou cabinet and was adopted by the Hellenic Parliament in May 2010. The programme's implementation started with the November 2010 local elections, and was completed by January 2011. It was amended by the Kleisthenis I Programme (Law 4555/2018), which was adopted in July 2018 and implemented in September 2019.