伊沙关系，又称沙伊关系（阿拉伯语：العلاقات الإيرانية السعودية，波斯語：روابط ایران و عربستان سعودی），是指伊朗伊斯蘭共和國和沙烏地阿拉伯王國之间的外交关系。雙方關係极为复杂，两国针对不同的地緣政治問題存在分歧，如對伊斯蘭教的解讀，對伊斯蘭世界领导权（遜尼派和什叶派）的争夺，石油出口政策以及與美國和其他西方國家的關係。雖然沙特阿拉伯和伊朗都是穆斯林多數國家，遵循《古兰经》中的教义进行統治，但由於政治議程的差異，以及信仰分歧加深，双方關係充斥着敵對，緊張和對抗。沙特阿拉伯是1932年建立的伊斯兰现代主义君主制国家，具有第二次世界大战后与美国和英国关系密切的传统。同时作为遜尼派为多数，且为伊斯兰教发源地的国家，在穆斯林世界中的逊尼派有极大的影响力。现代伊朗以前是一个成立于1925年的十二伊玛目什叶君主立宪制国家，同时作为什叶派为多数的国家，同样在穆斯林世界中的什叶派有极大的影响力。曾经这两个国家在美苏冷战中都与西方集團结盟，以防止苏联在这些国家的影响力。不过在1979年，伊朗爆发了伊朗伊斯兰革命后，其政治制度成为由“最高领袖”统治的，将神权政治和民主选举相结合的伊斯兰共和国，与西方关系开始交恶。沙特阿拉伯和伊朗都被視為對伊斯蘭教的領導願望，對穩定和區域秩序有著不同的看法。
^Commins, David. The Wahhabi Mission and Saudi Arabia. I.B.Tauris. 2009: 115. "Saudi Arabia lacks a constitution that defines legislative authority and processes. Wahhabi doctrine, however, possesses a political theory, based on the views of the Philosopher Ibn Taymiyya, which requires Muslims to obey the ruler, even if he is a sinner. Muhammad Ibn Abd al-Wahhab in the Book of God's Unity had declared that to obey the rulers in permitting something forbidden by Islamic law is tantamount to idolatry. In Ibn Taymiyya's view, the only ground for disobedience to a ruler is if he commands a believer to violate something prohibited by the shari'a.
^Commins, David. The Wahhabi Mission and Saudi Arabia. I.B.Tauris. 2009: 171. Tehran's efforts to export the revolution through leaflets, radio broadcasts and tape cassettes castigating Al Saud for corruption and hypocrisy found a receptive audience in the Eastern Province. On 28 November, Saudi Shiites summoned the courage to break the taboo on public religious expression by holding processions to celebrate the Islamic holy day of Ashura ... (both Sunni and Shia followers celebrate it but in different ways as per their individual beliefs, customs and rituals) ... on 1 February, the one-year anniversary of Ayatollah Khomeini's return to Iran, violent demonstrations again erupted. Crowds attacked banks and vehicles and hoisted placards with Khomeini's picture. The government responded to the February protests with a mix of coercion and cooptation. On the one hand, leading Shiite activists were arrested. On the other hand, a high official from the Interior Ministry met with Shiite representatives and acknowledged that Riyadh had neglected the region's development needs. ... extending electricity networks ... more schools and hospitals and improving sewage infrastructures.
