Fahd bin Abdulaziz Al Saud (Arabic: فهد بن عبد العزيز آل سعود Fahd ibn ʿAbd al ʿAzīz Āl Suʿūd, Najdi Arabic pronunciation: [fah(aː)d ben ˈʕabd alʕaˈziːz ʔaːl saˈʕuːd]; 1921 or 1923 – 1 August 2005) was a Saudi Arabian politician who was King of Saudi Arabia from 13 June 1982 until his death in 2005. Prior to his ascension, he was Crown Prince of Saudi Arabia from 25 March 1975 to 13 June 1982. He was the eighth son of King Abdulaziz, the founder of modern Saudi Arabia. He was also the fourth of Abdulaziz's six sons who were kings (the others were Saud, Faisal, Khalid, Abdullah and Salman).

Fahd was the eldest of the Sudairi Seven, the sons of King Abdulaziz by Hassa bint Ahmed Al Sudairi. He served as minister of education from 1953 to 1962 during the reign of King Saud. Afterwards he was minister of interior from 1962 to 1975, at the end of King Saud's reign and throughout King Faisal's reign. He was appointed crown prince when his half-brother Khalid became king following the assassination of King Faisal in 1975. Fahd was viewed as the de facto leader of the country during King Khalid's reign in part due to the latter's ill health.

Upon the death of King Khalid in 1982, Fahd ascended to the throne. He is credited for having introduced the Basic Law of Saudi Arabia in 1992. He suffered a debilitating stroke in 1995, after which he was unable to continue performing his full official duties. His half-brother Crown Prince Abdullah served as de facto regent of the kingdom and succeeded Fahd as king upon his death in 2005. With a reign of 23 years, Fahd remains the longest-reigning Saudi king.