General Muhammad Zia-ul-Haq HI, GCSJ, ร.ม.ภ, (Urdu: محمد ضیاء الحق; 12 August 1924 – 17 August 1988) was a Pakistani four-star general who became the sixth President of Pakistan following a coup and declaration of martial law in 1977. Zia served in office until his death in a plane crash in 1988. He remains the country's longest-serving de facto head of state and Chief of Army Staff.

Educated at St. Stephen's College, Delhi, Zia was commissioned in the British Indian Army in the Guides Cavalry on 12 May 1943 after graduating from the Officer Training School (OTS) Mhow as British Army Officer and fought against Japanese forces in World War II in Burma and Malaya, before opting for Pakistan in 1947. He fought as a tank commander in the Indo-Pakistani War of 1965. In 1970, he led a military training mission to Jordan, proving instrumental to defeating the Black September insurgency against King Hussein. In recognition, Prime Minister Zulfikar Ali Bhutto appointed Zia Chief of Army Staff in 1976 and awarded him the Hilal-i-Imtiaz medal.

Following civil disorder, Zia deposed Bhutto in a military coup and declared martial law on 5 July 1977. Bhutto was controversially tried by the Supreme Court and executed less than two years later for allegedly authorizing the murder of Nawab Muhammad Ahmed Khan Kasuri, a political opponent. Assuming the presidency in 1978, Zia played a major role in the Soviet–Afghan War. Backed by the United States and Saudi Arabia, Zia systematically coordinated the Afghan mujahideen against the Soviet occupation throughout the 1980s. This culminated in the Soviet Union's withdrawal in 1989, but also led to the proliferation of millions of refugees, with heroin and weaponry into Pakistan's frontier province.

Internationally Zia bolstered ties with China and the United States, and emphasized Pakistan's role in the Islamic world, while relations with India worsened amid the Siachen conflict and accusations that Pakistan was aiding the Khalistan movement. Domestically, Zia passed broad-ranging legislation as part of Pakistan's Islamization, curbed civil liberties, and heightened press censorship. He also escalated Pakistan's atomic bomb project, and instituted industrialization and deregulation, helping Pakistan's economy become the fastest-growing in South Asia, overseeing the highest GDP growth in the country's history. After lifting martial law and holding non-partisan elections in 1985, Zia appointed Muhammad Khan Junejo Prime Minister but accumulated more presidential powers via the Eighth Amendment to the Constitution. After Junejo signed the Geneva Accords in 1988 against Zia's wishes, and called for an inquiry into the Ojhri Camp disaster, Zia dismissed Junejo's government and announced fresh elections in November 1988. Muhammad Zia-ul-Haq was killed along with several of his top military officials and two American diplomats in a mysterious plane crash near Bahawalpur on 17 August 1988.

To this day, Zia remains a polarizing figure in Pakistan's history, credited with preventing wider Soviet incursions into the region as well as economic prosperity, but decried for weakening democratic institutions, passing laws encouraging religious intolerance, and depreciating the rupee with managed float policies. He is also cited for promoting the early political career of Nawaz Sharif, who would be thrice elected Prime Minister.

Zia is credited with stopping an expected Soviet invasion of Pakistan. Former Saudi intelligence chief Prince Turki Al-Faisal, who worked with Zia during the 1980s against the Soviets, described Zia in the following words: "He was a very steady and smart person with a geo-strategic mind, particularly after the invasion by Soviets. He was very dedicated in preventing the Soviet invasion of Pakistan."