Muhammad Zia-ul-Haq (12 August 1924 – 17 August 1988) was a Pakistani military officer and politician who served as the sixth president of Pakistan from 1978 until his death in an airplane crash in 1988. He also served as the second chief of the army staff of the Pakistan Army from 1976 until his death. The country's longest-serving de facto head of state and chief of the army staff, Zia's political ideology is known as Ziaism.

Born in Jalandhar, Punjab, Zia was trained at the Indian Military Academy in Dehradun and fought in the Second World War under the British Indian Army. Following the partition of India in 1947, he joined the Pakistan Army as a part of the Frontier Force Regiment. Zia was on active duty in Kashmir during the 1965 war between India and Pakistan, and after it he was promoted to colonel. During Black September, he played a prominent role as an advisor of the Jordanian Armed Forces against the Palestine Liberation Organization. In 1976, Zia was elevated to the rank of general and was appointed as chief of the army staff by Prime Minister Zulfikar Ali Bhutto, succeeding Tikka Khan. In July 1977, Zia organized Operation Fair Play, in which he overthrew Bhutto's federal government, declared martial law and assumed the office of the chief martial law administrator, dissolved the federal and provincial legislatures — hence suspending the provincial governments as well and declaring governor's rule across all provinces — and suspended the constitution. The coup was the second in Pakistan's history.

Zia remained de facto leader for over a year, assuming the presidency in September 1978, after Fazal Ilahi Chaudhry resigned. He directed a policy of Islamisation in Pakistan, escalated the country's atomic bomb project and instituted industrialisation and deregulation, which significantly improved Pakistan's economy. In 1979, following the Soviet invasion of Afghanistan, Zia adopted an anti-Soviet stance and aided the Afghan mujahideen. He bolstered ties with China and the United States, and emphasised Pakistan's role in the Islamic world. Zia held non-partisan elections in 1985 and appointed Muhammad Khan Junejo prime minister, though he accumulated more presidential powers through the Eighth Amendment to the Constitution. He dismissed Junejo's government on charges of economic stagflation and announced a general election in November 1988. However, on August 1988, while travelling from Bahawalpur to Islamabad, Zia died in an aircraft crash near the Sutlej River. He is buried at the Faisal Mosque in Islamabad.

Zia dominated Pakistan's politics for over a decade and his proxy war against the Soviet Union is credited with leading to a Taliban takeover. He is praised by right-wing conservatives for his desecularisation efforts and opposition to Western culture. Conversely, Zia's detractors criticise his authoritarianism, his press censorship, his purported religious intolerance, his suppression of women's rights by Hudood Ordinance, and his weakening of democracy in Pakistan.

Muhammad Zia-ul-Haq was born on 12 August 1924 in Jullundur, Punjab, British India. His father, Muhammad Akbar Ali, worked in the Army General Headquarters in Delhi. Ali was noted for his religiousness which earned him the Muslim clerical title of maulvi. His family belonged to the Arain community of Punjabis. At an early age, Zia and his six siblings were taught the Quran.

After completing his initial education in Simla, Zia attended Delhi's prestigious St. Stephen's College, an Anglican missionary school, for his bachelor's degree in history, from which he graduated with distinction in 1943. He was admitted to the Indian Military Academy at Dehradun, graduating in May 1945 among the last group of officers to be commissioned before the independence of India.

Zia was commissioned into the British Indian Army on 12 May 1943 after graduating from the Mhow Officer Training School. He was posted to the 13th Lancers, a cavalry unit accoutered with tanks. During the Second World War, in May 1945, Zia participated in the Burma campaign and the Malayan campaign of the Pacific War against the Imperial Japanese Army.

Zia also participated in Indonesian National Revolution and the Battle of Surabaya.