Michel Aflaq (Arabic: ميشيل عفلق, romanized: Mīšīl ʿAflaq‎, Arabic pronunciation: [miˈʃel ˈʕaflaq], 9 January 1910 – 23 June 1989) was a Syrian philosopher, sociologist and Arab nationalist. His ideas played a significant role in the development of Ba'athism and its political movement; he is considered by several Ba'athists to be the principal founder of Ba'athist thought. He published various books during his lifetime, the most notable being The Battle for One Destiny (1958) and The Struggle Against Distorting the Movement of Arab Revolution (1975).

Born into a middle-class family in Damascus, Syria, Aflaq studied at the Sorbonne, where he met his future political companion Salah al-Din al-Bitar. He returned to Syria in 1932, and began his political career in communist politics. Aflaq became a communist activist, but broke his ties with the communist movement when the Syrian–Lebanese Communist Party supported colonial policies through the Popular Front under the French Mandate of Syria. Later in 1940 Aflaq and al-Bitar established the Arab Ihya Movement (later renaming itself the Arab Ba'ath Movement, taking the name from Zaki al-Arsuzi's group by the same name). The movement proved successful, and in 1947 the Arab Ba'ath Movement merged with al-Arsuzi's Arab Ba'ath organisation to establish the Arab Ba'ath Party. Aflaq was elected to the party's executive committee and was elected "'Amid" (meaning the party's leader).

The Arab Ba'ath Party merged with Akram al-Hawrani's Arab Socialist Party to establish the Arab Socialist Ba'ath Party in 1952; Aflaq was elected the party's leader in 1954. During the mid-to-late 1950s the party began developing relations with Gamal Abdel Nasser, the President of Egypt, which eventually led to the establishment of the United Arab Republic (UAR). Nasser forced Aflaq to dissolve the party, which he did, but without consulting with party members. Shortly after the UAR's dissolution, Aflaq was reelected as Secretary General of the National Command of the Ba'ath Party. Following the 8th of March Revolution, Aflaq's position within the party was weakened to such an extent that he was forced to resign as the party's leader in 1965. Aflaq was ousted during the 1966 Syrian coup d'état, which led to a schism within the Ba'ath Party. He escaped to Lebanon, but later went to Iraq. In 1968 Aflaq was elected Secretary General of the Iraqi-led Ba'ath Party; during his tenure he held no de facto power. He held the post until his death on 23 June 1989.

Aflaq's theories about society, economics, and politics, which are collectively known as Ba'athism, hold that the Arab world needs to be unified into one Arab Nation in order to achieve an advanced state of development. He was critical of both capitalism and communism, and critical of Karl Marx's view of dialectical materialism as the only truth. Ba'athist thought placed much emphasis on liberty and Arab socialism – a socialism with Arab characteristics, which was not part of the international socialist movement as defined by the West. Aflaq believed in the separation of state and religion, and was a strong believer in secularisation, but was against atheism. Although a Christian, he believed Islam to be proof of "Arab genius". In the aftermath of the 1966 Ba'ath Party split, the Syrian-led Ba'ath Party accused Aflaq of stealing al-Arsuzi's ideas, calling him a "thief" and later sentenced him to "death via absentia" in 1971. The Iraqi-led Ba'ath Party rejects this, and does not believe that al-Arsuzi contributed to Ba'athist thought.