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Bilateral relations between Saudi Arabia and the United States began in 1933 when full diplomatic relations were established. These relations were formalized under the 1951 Mutual Defense Assistance Agreement. Despite the differences between the two countries—an Islamic absolute monarchy versus a secular constitutional republic—the two countries have been allies ever since. The U.S. provides military protection to the Kingdom in exchange for a reliable oil supply, pricing of oil in U.S. dollars, and support for American foreign policy.

Ever since the modern relationship began in 1945, the U.S. has been willing to overlook some of the kingdom's domestic and foreign policy aspects as long as it maintained oil production and supported American national security policies. These aspects include Wahhabism, its human rights record, and alleged state-sponsored terrorism. After the Soviet invasion of Afghanistan in 1979, the alliance deepened, as both countries jointly supported Afghan resistance militias during the 1980s. The Gulf War (1990–1991) marked a high point in the relationship when both countries and the UK jointly led an international military coalition in response to the Iraqi invasion of Kuwait. While the two countries continue to enjoy strong ties, critical disagreements have emerged over the years. Examples include Israel, the 1973 oil embargo, the 2003 U.S.-led invasion of Iraq, the "war on terror", and Saudi influence after the September 11 attacks. In recent years, particularly since the Barack Obama administration, the relationship has become strained and witnessed a major decline.

Saudi-U.S. relations were strengthened by the Trump administration's trip to Saudi Arabia in May 2017. In October 2018, Saudi dissident and Washington Post journalist Jamal Khashoggi was assassinated in a Saudi consulate in Turkey. This became a breaking point in relations and caused a serious rift between the two countries. The United States sanctioned some Saudi nationals, and Congress attempted to cut off U.S. weapons sales to Saudi Arabia related to the war in Yemen. However, this was unsuccessful due to opposition from the Trump administration. Turkish authorities and U.S. intelligence agencies concluded that the killing was ordered by Mohammed bin Salman, the crown prince of Saudi Arabia.

During his election campaign, Biden had pledged to make Saudi Arabia "a pariah". The Biden Administration emphasized its human rights policy as the key arbiter of the U.S. relationship with Saudi Arabia. Diplomatic relations hit a new low after a February 2021 U.S. intelligence report accused the crown prince of being directly involved in the assassination of Khashoggi. During Russia's invasion of Ukraine, Saudi Arabia defied U.S. efforts to isolate Vladimir Putin and instead strengthened relations with Russia by coordinating to reduce oil output of OPEC countries in October 2022. This event triggered a strong backlash in the United States, with relations sinking to an "all-time low" and tensions exacerbating further. American officials have criticized Saudi Arabia for actively enabling Russians to bypass US-EU sanctions and for undermining Western efforts to isolate Vladimir Putin. Saudi Arabia has also defied the United States' China containment policy. In December 2022, Saudi Arabia hosted Chinese leader Xi Jinping for a series of summits to sign a "comprehensive strategic partnership agreement" which elevated Sino-Arab relations. However, after Trump returned to the presidency in 2025, he chose to visit the Kingdom again as his first visit, while calming the friction caused by the previous administration.