Bilateral relations exist between the countries of Bahrain and Iran. Since the 1979 Iranian Revolution, relations between the two countries have been strained over various geopolitical issues such as the interpretations of Islam, aspirations for leadership of the Islamic world, and relations with the United States, Europe, and other Western countries. In addition, Iran has been severely critical of Bahrain for hosting the United States Fifth Fleet within the Persian Gulf at the Naval Support Activity Bahrain base.
After the Saudi diplomatic missions in Iran were ransacked by Iranian protesters following the execution of Nimr al-Nimr, Bahrain followed Saudi Arabia's decision by severing diplomatic relations with Iran on January 4, 2016. On 16 April 2019, a court in Bahrain sentenced 139 people to prison for forming terrorist groups backed by Iran. A total of 169 were arrested.
Relations under Pahlavi dynasty
Iran had a historic claim to Bahrain until March 1970 when Shah Mohammad Reza Pahlavi abandoned the claim as a result of secret Anglo-Iranian negotiations. Following this realignment of policy, the two countries signed a demarcation agreement in 1970.
Relations under the Islamic republic
Following the Iranian Revolution in which Ayatollah Khomeini came to power in Iran in 1979, Iran made clear its intention to export its Islamic revolution throughout the Muslim world, especially in the Arab world.
Two years later, Bahraini Shia fundamentalists orchestrated a coup attempt under the auspices of a front organization, the Islamic Front for the Liberation of Bahrain. The coup, which failed, would have installed a Shia cleric exiled in Iran, Hujjat al-Islam Hādī al-Mudarrisī, as the Supreme Leader of Bahrain with a theocratic government. The Bahraini government unofficially regarded the coup as Iran attempting to overthrow their Sunni government. Iran denied any involvement, saying the fundamentalists were inspired by the Iranian revolution but had received no support from Iran. Fearful of a recurrence, Bahrain cracked down on its Shia population, putting thousands into jail and further souring relations with Iran.
In November 2007, President Mahmoud Ahmadinejad of Iran made his first official visit to Bahrain and met with King Hamad bin Isa Al Khalifa. Ahmadinejad discussed future agreements to supply Bahrain with natural gas during his meeting with the king and Bahraini officials. Iran and Bahrain are beginning to enjoy closer relations again and have engaged in many joint economic ventures.
In the aftermath of the March 2011 protests in Bahrain, Iran expressed strong support for the demonstrators, the majority of whom follow Shia Islam, which is Iran's state religion. Relations between Tehran and Manama cooled considerably during the uprising, with both countries expelling one another's ambassadors. Iran was joined by Iraq in opposing the Gulf Cooperation Council's military intervention in Bahrain. Allies of the Bahraini government, such as Saudi Arabia and other GCC member states, have conversely blamed Iran for inciting upheaval in the small archipelago country and questioned the legitimacy of the protesters' demands, echoing Manama's claims.
On 12 August 2012, Foreign Minister of Bahrain Sheikh Khalid al-Khalifa announced from his Twitter account that Bahrain had reinstated its ambassador to Iran, nearly 18 months after relations between the two countries were strained following the 2011 Bahrain protests.
On 19 July 2015, after Supreme Leader Ali Khamenei voiced support for the oppressed people across the Middle East, including Bahrain, the Iranian acting chargé d'affaires Morteza Sanubari was summoned by the Foreign Minister of Bahrain over "flagrant interference". The foreign minister handed "an official protest memorandum" to the diplomat over "statements made by Ali Khamenei against the Kingdom of Bahrain".
On 13 August 2015, the Bahrain Interior Ministry announced arresting of five members of a terrorist group which was linked to at least one bombing attack in Sitra and was believed to accept aid and training from Lebanese militant group Hezbollah and Iran's Islamic Revolutionary Guard Corps (IRGC).