Gas Hub Formation Under Regulatory Constraints: Türkiye and the EU’s Russian Gas Phase-Out

States located between gas producers and consumers have long sought to become regional trading hubs. This article examines what limits such transit states and how the European Union’s (EU) phase-out of Russian gas affects hub formation on its periphery. Drawing on interdependence, transit-bargaining, and hub-maturity theories, it distinguishes three dimensions of hub status: physical optionality, market depth, and political–regulatory acceptance. The framework is applied to Türkiye through process tracing of contracts, official statements, EU legislation, and market, price, and flow data for 2018–2026. Türkiye’s import capacity and contracted supply expanded after 2022, but supply remained concentrated by origin. No liquid, price-forming wholesale market emerged: voluntary trading in the organised market fell sharply from 2021 and did not recover when domestic prices approached European hub levels, and the domestic reference price does not track the Dutch Title Transfer Facility (TTF) hub price from month to month. Regulation (EU) 2026/261 adds a market-access constraint: flows from Türkiye at the Strandzha 1 entry point fell sharply in 2026, although this cannot yet be separated from commercial factors. The article characterises Türkiye with the typological label “portfolio transit state”, contrasts it with Ukraine, Greece, and Bulgaria, and derives expectations for comparative research.