Three Seas, One Coastline: Türkiye's Maritime Jurisdiction in the Aegean, Black Sea and Mediterranean

Why It Matters

Türkiye treats its maritime jurisdiction as one connected case across three seas (the Black Sea, the Aegean and the Eastern Mediterranean), and the 2025 Marine Spatial Planning of the Republic of Türkiye is the first document to set out that position across all three. It was unveiled on 16 April 2025 and recorded with the Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) on 12 June 2025. It matters to diplomats, energy professionals and lawyers because it shows where Ankara's position rests on settled treaties (mainly the Black Sea) and where it is contested (the Aegean and the Eastern Mediterranean).

This guide applies a ‘meridian’ reading to the Blue Homeland (Mavi Vatan). Ankara sees the Black Sea, the Aegean and the Eastern Mediterranean as one continuous coastal frontage, not three separate files, and the guide follows that line through the law, the documents and the competing positions. For readers who want the generic Blue Homeland primer, see The Political Anatomy's complete guide or Crossroads Review's explainer. This page focuses on the three-sea architecture and the 2025 planning instrument.

Background

The meridian logic: one coastline, three seas

Türkiye's coastline runs along the Black Sea in the north, the Aegean in the west and the Mediterranean in the south, and is commonly cited at roughly 8,300 km in total. Its Mediterranean frontage of 870 km is the longest continental coast in the Eastern Mediterranean. The term Mavi Vatan was popularised in Turkish naval circles from 2006 (it is associated with Admiral Cem Gürdeniz). Official documents speak of ‘maritime jurisdiction areas’ rather than a territorial claim, and Ankara's stated aim is delimitation by agreement on equitable principles. For the geographic logic behind this, see Türkiye's Strategic Meridian.

The three seas have different legal characters:

Chronology of the main instruments

The legal toolkit

The main legal sources are the 1958 Geneva Convention on the Continental Shelf, the 1982 UN Convention on the Law of the Sea (UNCLOS), customary international law and ICJ and arbitral case law. Articles 74 and 83 of UNCLOS require delimitation of EEZ and continental shelf ‘by agreement on the basis of international law’ to reach an ‘equitable solution’. Greece, the Greek Cypriot administration and the EU treat UNCLOS as binding or as customary law. Türkiye, not a party, relies on equity, special circumstances and the conduct of the parties. Both sides agree that delimitation should lead to an equitable result. They disagree on how much weight islands deserve.

Case law matters because it shows how courts treat islands:

• North Sea Continental Shelf (ICJ, 1969) stressed equitable principles and the natural prolongation of land territory.
• The Anglo-French Arbitration (1977) gave the Channel Islands, which lie close to France, a reduced effect.
• Libya/Malta (ICJ, 1985) and Romania v. Ukraine (ICJ, 2009) applied proportionality checks, and the latter gave Serpents' Island no effect on the delimitation line beyond its territorial sea.

Greek and Greek Cypriot sources read these cases differently. They argue that Article 121(2) of UNCLOS gives inhabited islands the same entitlements as other land territory, and that rulings that reduced island effect turned on specific facts. For a direct treatment of the island question, see the fact check on islands and the continental shelf and The Worldlogue's analysis of the equity principle.

From filings to fleet: how the position was built

The 2004 UN notifications recorded Türkiye's continental shelf coordinates in the Eastern Mediterranean. TPAO (Türkiye's national petroleum company) licences in 2009 and 2012 added a field presence. The 21 September 2011 agreement with the TRNC delimited the shelf between the two sides, two days after the Greek Cypriot administration began unilateral drilling. The Türkiye–Libya memorandum of 27 November 2019 delimited the maritime zones between the Turkish and Libyan coasts, and the 18 March 2020 submission to the UN registered Türkiye's outer limits. The legal basis and the reactions are covered in the 2019 Türkiye–Libya memorandum guide.

On the water, Türkiye relies on a national fleet. The deep-sea drilling vessels are Fatih, Yavuz, Kanuni and Abdülhamid Han. The seismic survey vessels are Oruç Reis and Barbaros Hayreddin Paşa. Official Turkish accounts list eight major Eastern Mediterranean wells: Alanya-1, Finike-1, Karpaz-1, Güzelyurt-1, Mağusa-1, Narlıkuyu-1, Lefkoşa-1 and Selçuklu-1. In the Black Sea, the Tuna-1 discovery announced in August 2020 led to the Sakarya gas field, which began first production in April 2023.

The 2025 planning instrument

Marine spatial planning is a standard tool through which states organise uses of their sea space (shipping, fisheries, energy, conservation and defence). The plan unveiled on 16 April 2025 covers the Black Sea, the Aegean and the Mediterranean in one document, and a Marine Protected Area was designated off Finike. After the plan was recorded with IOC-UNESCO on 12 June 2025, the Presidential Circular of 24 July 2025 created an Inter-Agency Coordination Board under the Ministry of Foreign Affairs to coordinate its implementation.

The legal meaning of the recording is itself debated. Ankara presents it as the first time its position across the three seas has been entered in the record of a UN body. Critics note that IOC-UNESCO's planning portals work as information repositories and do not endorse the boundary positions they contain. Both readings are consistent with the documents. The recording gives Türkiye's position a formal home in a UN setting, but it does not create a boundary on its own.

Key Players & Positions

Greece

According to the Greek Ministry of Foreign Affairs, Greece is a party to UNCLOS and holds that all islands, including small inhabited ones, generate territorial waters, a continental shelf and an EEZ. Athens says the only dispute with Türkiye is the delimitation of the continental shelf and EEZ, and that it should go to the International Court of Justice. Greece retains the right to extend its Aegean territorial waters from 6 to 12 nautical miles. Greek officials rejected the 2019 Türkiye–Libya memorandum as ignoring the Greek islands, notably Crete, and signed the partial EEZ agreement with Egypt in August 2020. Greece has also adopted its own national maritime spatial plan and announced marine parks, and Greek officials have objected to the Turkish plan where it overlaps with zones Athens claims. In December 2023 Athens and Ankara signed the Athens Declaration on friendly relations and good neighbourliness, which set out a calmer track without resolving the legal dispute.

The Greek Cypriot administration

The Republic of Cyprus, in practice governed by the Greek Cypriot side, enacted an EEZ law in 2004 and signed delimitation agreements with Egypt (2003), Lebanon (2007) and Israel (2010). Nicosia says it acts within UNCLOS and denies that Türkiye has a basis to object. Its officials say that Turkish Cypriots will benefit from hydrocarbon resources after a settlement, and in 2019 President Anastasiades proposed a fund for that purpose. The Turkish Cypriot side and Ankara reject these arrangements, as set out below.

Egypt

Egypt relies on its 2003 agreement with Cyprus and its 2020 partial agreement with Greece. Cairo's foreign ministry rejected the Türkiye–Libya memorandum as legally ineffective for third parties. Egypt and Türkiye have normalised ties since 2023 and exchanged presidential visits in 2024. The East Mediterranean Gas Forum, established in Cairo in 2019 and formalised in 2020, does not include Türkiye or the TRNC. Egyptian sources describe it as a cooperation forum rather than a bloc against any state.

The European Union

The European Council's conclusions of 12 December 2019 stated that the Türkiye–Libya memorandum infringes the sovereign rights of third states, does not comply with UNCLOS and cannot produce legal consequences for third states. EU institutions have also expressed solidarity with Greece and Cyprus. In February 2020 the EU listed two TPAO executives under its sanctions framework over drilling activities. Brussels maintains that it is acting on the rights of its members, and Ankara says that the EU is not a competent authority for delimitation.

Libya and other coastal states

The Government of National Accord signed the 2019 memorandum, and Libyan institutions have since disagreed over its status. Israel and Lebanon have their own bilateral and domestic positions and overlapping interests in the same basin.

Source Comparison

The same documents are read differently depending on the source. The table sets out common framings against the primary documents a reader can check.

Three habits are worth watching when reading coverage. First, headlines often describe ‘Turkish claims’ without distinguishing Black Sea treaties, which are settled, from the Aegean and Eastern Mediterranean, where the parties differ. Second, coverage may treat the EU's political support as a legal determination of boundaries. Third, the Turkish Cypriot dimension is frequently absent from non-Turkish summaries. Reading the original treaty texts, UN notifications and ministry statements side by side is the most reliable corrective. The site's editorial principles explain how this publication attributes positions.

Key Terms & Related Guides

• Blue Homeland (Mavi Vatan): A concept from Turkish naval thinking that describes Türkiye's maritime jurisdiction areas across the Black Sea, the Aegean and the Mediterranean. Official policy is framed as delimitation by agreement.
• Continental shelf: The seabed and subsoil that extend from a coastal state's land territory. Coastal states hold sovereign rights over its resources.
• EEZ (exclusive economic zone): A zone up to 200 nautical miles (about 370 km) where the coastal state has sovereign rights over resources. It differs from the continental shelf in legal source and content.
• Equity principle: The requirement that delimitation reach an equitable result, which courts apply with checks such as proportionality.
• Marine spatial planning (MSP): A public process for allocating the uses of marine space. IOC-UNESCO promotes it internationally, and Türkiye's 2025 plan was recorded in that framework.
• TPAO: Türkiye's national petroleum company, which holds exploration licences.
• TRNC: The Turkish Republic of Northern Cyprus, proclaimed on 15 November 1983. Ankara treats Turkish Cypriots as co-founders of the 1960 Republic.

Related guides on this site:

• Fact Check: Can a Few Small Islands Cancel the Continental Shelf of a Country with the Longest Coastline?
• The 2019 Türkiye–Libya Maritime Memorandum
• Cyprus on the Strategic Line
• Türkiye's Strategic Meridian
• Montreux Article 19 and the Black Sea

For sister-publication analysis, see Monitor of Nations on equity and the law of the sea. Readers can also learn more in the About section and the FAQ on sources and methodology.

Perspective Note

The Strategic Meridian presents global affairs with a dedicated perspective from Türkiye. Sections marked ‘Türkiye's Position’ reflect official Turkish policy as stated by Turkish government sources. The Strategic Meridian is an editorial publication that presents analysis from a Türkiye-informed perspective on regional security, maritime law and history. Claims are attributed to primary sources such as treaties, UN documents, official archives and legal texts, and readers are encouraged to consult them directly. Published by The Strategic Meridian Editorial Team.