As an ally of the United States, Saudi Arabia’s relations with Iran have been strained since the Islamic Revolution in 1979. Despite having similar oil-based economies and sharing common membership in international organizations such as the Organization of Petroleum Exporting Countries, the Organization of the Islamic Conference and the Non-Aligned Movement, Saudi Arabia and Iran have often found themselves in political competition and engaged in proxy conflicts across the greater Middle East. In 1979, Saudi Arabia’s minority Shi’a, inspired by Ayatollah Khomeini’s calls for revolutionary uprisings in the region, began staging protests in the Kingdom’s Eastern Province that eventually resulted in a number of deaths. In 1987 after 400 people, including 275 Iranians, died following a riot instigated by Iranian pilgrims in Mecca, Ayatollah Khomeni demanded the overthrow of the Saudi monarchy. Several bomb attacks on Saudi facilities abroad and assassinations of Saudi diplomats during this period were connected to Saudi Shi’a supported by the Islamic Republic. The Saudi government accused Iran of two bombings in 1989 thought to be in revenge for quotas imposed by Saudi officials on Iranians traveling to Mecca. In 1996, Saudi Hezbollah operatives directed, trained, and supported by the Iranian government bombed the Khobar Towers facility in Saudi Arabia, killing 19 American servicemen. Most recently, Saudi Arabia deployed several hundred troops to Bahrain to put down the Shi’a-led protests that the Riyadh-based Gulf Cooperation Council believed were instigated by Iran.
During the Iran-Iraq War (1980-1988), Saudi Arabia supported Saddam Hussein against Iran, and although Saudi Arabia allied with the United States and coalition forces against Iraq during the 1990-1991 Gulf War, subsequent regional security arrangements between Saudi Arabia and the United States further stressed its ties with Iran. 
In recent years, Saudi Arabia has publicly questioned the peaceful nature of Iran’s nuclear enrichment program. Indeed, Saudi Arabia’s opposition to Iran’s nuclear program has generated speculation that the country might endorse military action against Iran should diplomatic approaches fail. In June 2011, a senior Saudi official suggested that Saudi Arabia would pursue its own nuclear weapons program if Iran developed a nuclear weapon.
July 11, 2011: Officials of Saudi Arabian Oil Co., the state-owned oil company, suggested that Saudi Arabia could provide crude oil to India in order to make up for shortages resulting from a payment dispute between Iran and India. International sanctions placed on Iran over its nuclear program have inhibited the ability of oil refineries in India to locate banks willing to transfer payments to Iran.
June 22, 2011: Former Saudi intelligence chief and ambassador to Washington, Prince Turki al-Faisal, suggested that Iran’s oil sector was vulnerable, and that this could be exploited to pressure Iran from pursuing its nuclear program. He backed this assertion by claiming, “Saudi Arabia has so much [spare] production capacity—nearly 4 million barrels [per] day—that we could almost instantly replace all of Iran's oil production,” were there a reduction in Iran’s oil exports. In an address to NATO officials in the U.K., Faisal added that Iran’s acquisition of a nuclear weapon “would compel Saudi Arabia…to pursue policies which could lead to untold and possible dramatic consequences.”
March 11, 2010: U.S. Defense Secretary Robert Gates announced that Saudi Arabia was willing to press China on endorsing the new round of sanctions against Iran. Following a series of meetings with Saudi officials, Gates said that the talks had examined "how we bring pressure on the Iranian government to change its policies." The defense secretary suggested Saudi Arabia was in agreement: "I think there is an understanding that we have to try this. This is the next step." Official sources quoted by the Saudi Press Agency, however, denied that the Kingdom agreed to undertake any such efforts. An unnamed Saudi official claimed that “this issue [about Iran sanctions] is not true. It was not discussed during the visit of the Secretary of Defense who was in the Kingdom recently.” China ultimately voted in favor of United Nations Security Council Resolution 1929 on June 9, 2010.
October 7, 2009: Iran’s foreign minister accused the United States of apprehending Iranian nuclear scientist Shahram Amiri while he visited Saudi Arabia on a pilgrimage to Mecca. Iranian foreign minister Manoucher Mottaki claimed “We have evidence of a U.S. role in [the] disappearance of the Iranian national…in Saudi Arabia.” Iranian officials also later implicated Saudi Arabia in the kidnapping.
May 27, 2009: Saudi Arabian ministers participated in a major international conference on foreign investment in Iran.
July 10, 2011: Iranian Foreign Minister Ali Akbar Salehi stated that Iran hopes to improve ties with Saudi Arabia. He added, "We have had good and deep ties with Saudi Arabia. Current misunderstandings on regional developments can be settled. We need to find ways to carry out the consultations. We are in consultations and we hope bilateral Iran-Saudi Arabia dialogue on regional matters will take place in future."
July 2, 2011: The six GCC member states, including Saudi Arabia, unanimously approved an internal proposal to bolster their combined military force, the Peninsula Shield. The proposal would increase it troop levels from 50,000 to 100,000 by the end of 2012. Security, defense and intelligence advisor, Dr. Sami Alfaraj, stated that the decision was made in order to counter a growing threat from Iran “and its subversive terrorist elements across the GCC.”
June 29, 2011: Following a meeting between senior NATO military officials and former ambassador to Washington and chief of Saudi intelligence Prince Turki al-Faisal warned that a nuclear-armed Iran “would compel Saudi Arabia…to pursue policies which could lead to untold and possibly dramatic consequences.” He went on to criticize Iran for meddling in the affairs of Bahrain, Iraq, Lebanon, and Syria. Following the meeting, a senior Saudi official close to al-Faisal affirmed the Prince’s comments, stating that “[Saudi Arabia] cannot live in a situation where Iran has nuclear weapons and we don't. It's as simple as that…. If Iran develops a nuclear weapon, that will be unacceptable to us and we will have to follow suit.”
April 20, 2011: Both sides participating in the 21st session of the Joint Council for the European Union and the Saudi-based Gulf Cooperation Council called on Iran to desist from interfering in the internal affairs of Gulf countries.
March 14, 2011: Saudi Arabia deployed several hundred troops to Bahrain to defend government facilities and help put down protests led by Bahrain’s majority Shi’ite population. The Gulf Cooperation Council (GCC) claimed that the protests were instigated by Iran and chastised the Islamic Republic for “interference in the internal affairs of Bahrain.”
June 27, 2010: Saudi Arabia awarded a $1.7 billion contract to Raytheon Corporation to upgrade its Patriot air-defense systems, reportedly to “counter Iran’s power.”
July 19, 2010: Iranian Judiciary Chief Ayatollah Sadeq Larijani met with Saudi Arabia’s ambassador to Iran. During their talks, Larijani encouraged the two countries to expand bilateral ties, suggesting that cooperation in judicial matters could serve to strengthen relations between Iran and Saudi Arabia. The Iranian chief further argued in favor of establishing a committee of judicial chiefs from Islamic countries.
June 14, 2010: An official source at the Saudi Ministry of Foreign Affairs denied reports that it had granted permission to Israel to use its airspace to attack Iran, adding that the Saudis had a “clear stance that it would never allow anyone to use its airspace or territory to attack any other country.”
June 13, 2010: President Ahmadinejad, in a meeting with Saudi Ambassador Mohammed Ibn Abbas al-Kallabi, urged the two countries to remember their common religious identity and resist efforts by hostile actors to separate them. The Iranian president stated that "Iran and Saudi Arabia should take the side of each other given their common religion, outstanding position and common interests and enemies.” Ahmadinejad added: “the cultural, religious, political, international and economic grounds and defense of Muslims' rights are the opportunities which both countries can seize for expanding their mutual cooperation.”
May 23, 2010: Iranian Foreign Minister Manouchehr Mottaki met with Saudi Arabia’s ambassador to Iran Mohammad bin Abbas bin Hamza al-Kalabi and asserted that “wide interaction between [Saudi Arabia and Iran] will increase regional cooperation and remove the problems of the Muslim world…. The Islamic Republic of Iran and Saudi Arabia are two important states at regional and international levels and play a strategic role in resolving regional problems."
May 20, 2010: Saudi Deputy Foreign Minister Nizar Madani and Iranian Foreign Minister Manouchehr Mottaki met in Dushanbe, Tajistan on the sidelines of the Organization of the Islamic Conference foreign ministers meeting. The two discussed bilateral ties between Iran and Saudi Arabia.
January 19, 2010: Iranian Foreign Minister Manoucher Mottaki described Iran and Saudi Arabia as two important countries in the Middle East and the Islamic world. The minister went on to say that “Iran and Saudi Arabia, along with other Islamic nations, can take important steps towards resolving problems facing the Islamic world."
January 14, 2010: Speaking in Ahvaz, Iran, President Ahmadinejad stated that the Saudi actions in Yemen were part of a plot against Muslims. Ahmadinejad further added that “it was expected that … [Saudi Arabia] would enter in Yemen domestic conflict to create peace and friendship, not to enter the war and use weapons against Muslims.” In response, Saudi Arabia’s foreign minister Prince Saud denied that Saudi Arabia was involved in the Yemeni conflict and contended that in fact Iran was responsible for the turmoil.
January 2, 2010: Iran refused to remove the words "Persian Gulf" from the Islamic Solidarity Games’ promotional materials and medals. This decision caused the Riyadh-based Islamic Solidarity Games Federation to cancel the event. The committee accused Iran of taking unilateral decisions "by writing some slogans" on the medals and pamphlets. The games were scheduled to be held in Tehran in April.
January 2, 2010: Foreign Minister Prince Saud confirmed that Tehran and Riyadh have begun talks concerning the repatriation of Osama bin Laden’s daughter while she sought asylum in the Saudi embassy in Tehran. Several of bin Laden’s children and one of his wive’s crossed the Afghan-Iranian border in 2001 and have since lived under house-arrest.
November 12, 2009: After a Saudi Arabian air raid against Shi’a rebels operating in Yemen, Iran warned Saudi Arabia to halt support of the Yemeni military’s actions against the insurgents. Following the Saudi attack, Iranian Foreign Minister Manouchehr Mottaki warned that “those who pour oil on the fire must know that they will not be spared from the smoke that billows.”
August 9, 2009: Spokesman of Iran's Aviation Organization Reza Jafarzadeh announced that all flights to Saudi Arabia would cease throughout the holy month of Ramadan, citing an H1N1 flu outbreak in Saudi Arabia.
July 27, 2009: Iranian Foreign Minister Manouchehr Mottaki summoned Saudi Ambassador Osama bin Ahmad al-Sonosi to discuss “Saudi police misbehavior with Iranian pilgrims” visiting Saudi Arabia. The summons came after Saudi authorities fingerprinted Iranian women arriving at Jeddah International Airport. The row over the treatment of Iranian pilgrims in the Saudi Kingdom continued to escalate in the month of July, leading to heavy criticism by the head of Iran’s pilgrimage office in Saudi Arabia, Hassan Saqaie. Saqaie claimed that abuses by the Saudi “morality forces” have increased noticeably recently: "not only do [the morality forces] limit the religious activities of clerics, but they make false accusations against pilgrims and ask them to sign papers stating that they would not repeat the so called offenses."  The pilgrimage head called upon Saudi authorities to take steps to reduce abuses.
June 3, 2009: U.S. President Barack Obama met with Saudi King Abdullah to discuss Saudi concerns over the Iranian nuclear program and reiterate the two countries friendly diplomatic relations.