Ba'athism, also spelled Baathism, is an Arab nationalist ideology which advocates the establishment of a unified Arab state through the rule of a Ba'athist vanguard party operating under a revolutionary socialist framework. The ideology is officially based on the theories of the Syrian intellectuals Michel Aflaq (per the Iraqi-led Ba'ath Party), Zaki al-Arsuzi (per the Syrian-led Ba'ath Party), and Salah al-Din al-Bitar. Ba'athist leaders of the modern era include the former president of Iraq Saddam Hussein, and former presidents of Syria Hafez al-Assad and his son Bashar al-Assad.
The Ba'athist ideology advocates the "enlightenment of the Arabs" as well as the renaissance of their culture, values and society. It also advocates the creation of one-party states and rejects political pluralism in an unspecified length of time—the Ba'ath party theoretically uses an unspecified amount of time to develop an "enlightened" Arab society. Ba'athism is founded on the principles of Arab nationalism, pan-Arabism, and Arab socialism, as exemplified by its slogan "Unity, Freedom, Socialism".
Ba'athism advocates socialist economic policies such as state ownership of natural resources, protectionism, distribution of lands to peasants, and planned economies. Although inspired by Western socialist thinkers, early Ba'athist theoreticians rejected the Marxist class-struggle concept, arguing that it hampers Arab unity. Ba'athists contend that socialism is the only way to develop modern Arab society and unite it.
The two Ba'athist states which existed—Iraq and Syria—attempted to prevent criticism of their ideology through authoritarian means of governance. Ba'athist Syria's state ideology was neo-Ba'athism, a far-left form of Ba'athist ideology developed by the Assadist leadership of the Syrian Ba'ath party, which was quite distinct from the Ba'athism which Aflaq and Bitar wrote about. The Iraqi Ba'ath Party, meanwhile, was dominated by Saddamism, which had a more right-wing political orientation, culminating in an inter-Ba'athist conflict between the two Ba'athist states. Both Ba'athist regimes were ousted from power as a result of the U.S.-led invasion of Iraq in 2003 and the renewed rebel offensive in Syria in 2024 amid the Syrian civil war.