The Interconnecting Pipeline Greece-Bulgaria Project (IGB) consists of a pipeline with approximate length of 182 km (of which 31 km lies within Greek territory), as well as its supporting installations (metering stations, valve stations, operations centre). Stretching from Komotini, Greece to Stara Zagora, Bulgaria, the Greece-Bulgaria Interconnector (IGB) is a bi-directional natural gas pipeline connecting the national transmission networks of the two countries, as well as the TAP pipeline. It serves as the primary entry point and the cornerstone of the Vertical Gas Corridor, establishing energy links between Greece, Bulgaria, Romania, Moldova, and Ukraine. The IGB pipeline has an initial annual capacity of 3 billion cubic meters (bcm of natural gas) with the potential to increase it to 5 bcm annually by constructing a compressor station.

The implementation of the IGB project aims to diversify both natural gas routes and sources for Bulgaria and the wider region, transforming the Bulgarian energy market landscape through its capacity to boost competition and lower prices for consumers.

It should be noted that both Greece and Bulgaria actively support this project by labelling it as Project of National Importance and Public Interest (Greece: Legislation 400/2011, Article 176, Bulgaria: Cabinet Decision no. 452 dated 07.06.2012). Moreover, on 10 October 2020 an Intergovernmental Agreement was signed by the Minister of Energy and Environment of Greece Mr. Chatzidakis and the Minister of Energy of Bulgaria Ms. Temenuzhka Petkova.

In addition to that, the EU has included the project in its 5th list of Projects of Common Interest (PCI 5th list) based on European Regulation 347/2013. It is also included in the list of priority projects of the Central and Southeastern Europe Gas Connectivity initiative (CESEC).

In 2018, the EU approved the compatibility of the project's financial design and its tax regime under state aid rules. Total grants of €84 million are expected to be awarded from the European Energy Programme for Recovery (EEPR) and the Bulgarian European Structural & Investment Funds (ESIF). In addition, the National Regulatory Authorities of Greece and Bulgaria, with the agreement of the European Commission, granted the pipeline a Third-Party Access Exemption (TPA Exemption).

The Final Investment Decision for the implementation of the IGB Project was taken on 10 December 2015. Following the completion of the relevant International Tenders, in March 2019, the Owner's Engineer services - Project Management, Supervision and Inspection (TPI) services - were awarded, while in May 2019 the tenders were completed and the services for the Pipeline Procurement and Construction Contract (EPC - Engineering Procurement & Construction) were awarded.

On 22 May 2019, the construction opening ceremony took place in Kirkovo, Bulgaria. Construction work was completed in 2022 and the project was put into commercial operation on 1 October 2022.

The IGB pipeline has received permits from the Regulatory Authorities involved and operates as an Independent Gas System. Furthermore, the assessment of the capacity expansion potential to 5 bcm of natural gas is already underway, aiming to investigate the relevant technical and commercial parameters, as well as the possibilities for further utilization of the existing infrastructure.