Introduction: During recent decades, Iran and Turkmenistan have become reliable neighbours. But when these two countries want to develop their cooperation in the field of energy and export their gas to Europe through Turkey, they face different obstacles and challenges in issues such as bilateral relations, the Turkish energy market and the European Union. The purpose of this research is to examine the situation of Iran and Turkmenistan in the field of energy and the issue of gas transit to Europe through Turkey.
Research Question: The main question is, what are the opportunities and challenges of Turkmenistan gas transit from Iran and Turkey to Europe?
Research Hypothesis: The hypothesis of this research is based on the positive relations between Turkey, Iran and Turkmenistan and the geopolitical position of Iran, the connection with the opportunities and sanctions of the United States on Iran's energy sector, Russia's pressure on Turkmenistan for the exclusive purchase of gas, which is the most important challenge for the transit of gas from Turkmenistan to Europe.
Methodology (and theoretical framework if there are): In this paper, the qualitative research method for studying the hypothesis is based on Peter McLaughlin’s functional explanation. The data collection tool is based on library and internet resources. The theoretical framework of this research is based on the regional system proposed by Louis Cantori and Steven Spiegel. By combining this framework with functionalism, it examines the cooperation and competition of governments and analyzes the factors of convergence and divergence in the relations of these countries.
Results and Discussion: The analysis of this research shows that Iran and Turkmenistan have expanded their economic relations. The opening of the Mashhad-Sarkhs-Tajan railway lines and the Bafaq-Bandar Abbas railway line is considered as an important economic measure for the development of economic and trade relations between Iran and Turkmenistan. Also, the cooperation of the two countries in technical and engineering projects with numerous investments of Iranian technicians in this field has also been important.  Iran and Turkmenistan pursue their economic cooperation within the framework of the Joint Economic Commission. The main export of goods from Iran is related to Turkmenistan, and since 2013, the volume of trade between the two countries has increased, especially with Khorasan Razavi Province.With 5900 industrial units, 46 mineral resources and approximately 800 mines, Khorasan Razavi province has a high rank in the production of products such as saffron, pistachios, pomegranates and medicinal plants and mainly exports these products to Turkmenistan. The implementation of the border-crossing-permit plan between Iran and Turkmenistan has also provided the basis for the movement of nationals of both countries in the border areas.
Turkmenistan’s gas reserves are scattered throughout the country. In addition to the huge gas resources and significant production in this country, the discovery of Yultan gas field near Iran's Daulatabad field has put Turkmenistan in the focus of Iran's attention. The desire of Iran and Turkmenistan to cooperate made Turkmenistan agree to the construction of the country's first pipeline in July 1995. The Kerpcheh-Kordkoy pipeline was built in 1997 at a cost of over $200 million to transport gas to northern Iran from the Kerpcheh gas field. With abundant gas resources, Turkmenistan negotiated with Iran to export gas from Iran to Europe via Turkey. Due to its geopolitical position, Turkey has become an energy pole and this has created an opportunity for this country to gain more economic benefits. The European Union (EU) has become heavily dependent on foreign energy resources in recent decades.
Due to its geopolitical position, Turkey has become an energy hub that connects the Middle East, Russia and Europe. Many gas pipelines pass through Turkey, transporting gas from Central Asia and the Middle East to Europe. However, some of these pipeline projects have been suspended for some time. Turkey has given the green light to Iran’s presence in the Turkish gas market (to Europe) and the Tabriz–Ankara pipeline operates in this direction.
 
Conclusion: The findings indicate that first, long borders and economic capacities in Turkmenistan are like the gateway for Iran to enter this country and the two countries have cooperated in the field of natural gas transportation projects. Second, Turkmenistan’s rich gas resources and various gas fields led this country to build the first Kerpcheh-Kordkoy gas pipeline with Iran, which met the gas consumption needs of Iran’s northern provinces. Simultaneously with the construction of this pipeline, the issue of Turkmenistan gas transit from Iran to Turkey was raised so that Iran would receive transit rights. With Najmuddin Arbakan coming to power in Turkey in 1997, bilateral relations between Iran and Turkey improved significantly and Turkey's economic growth has led to an increasing need for gas imports. In this regard, Turkey has increased its gas transit pipelines in recent years. Europe's effort to diversify its gas imports from exporting countries and not relying only on Russia has provided the opportunity for Turkey to become the energy hub of the region by importing gas from Iran (and even other countries) and using its geopolitical position to re-export energy and gas to European markets. The improvement of relations between Iran and Turkey and the transit of gas to Europe have strengthened their economic growth, but the US sanctions against Iran and possible obstruction of gas exports by Iran in the case of incresing US pressure, may prevent them from making profits in their bilateral transactions.