Ignaz Seipel (19 July 1876 – 2 August 1932) was an Austrian Catholic priest and conservative politician, who served as the Chancellor of the First Austrian Republic twice during the 1920s and leader of the Christian Social Party. He is considered the most prominent statesman of the Austrian right in the interwar period.

Born into a modest bourgeois family, Seipel grew up in the town of Meidling, near Vienna, where he completed his studies before enrolling at the University of Vienna. He studied theology and was ordained as a priest in 1899. After serving in a rural parish, he returned to the imperial capital to pursue a doctorate. In 1908, he became an assistant professor of moral theology at the University of Vienna, and a year later, a full professor of the same discipline at the University of Salzburg, where he taught for the next eight years.

Seipel took an interest in social, educational, and economic issues and became friends with Heinrich Lammasch, a prominent Austrian jurist and the last Imperial Minister-President, who appointed him Minister of Social Welfare in his cabinet in late 1918. Although a monarchist, Seipel played a key role in helping the Christian Socialists accept the new republican system. He built up political Catholicism by aligning the clericals with Vienna's large bourgeoisie, often of Jewish descent. Over time, his political stance evolved: while initially a strong supporter of the Austria–Hungary and the Habsburg dynasty, after World War I, he adopted a conciliatory approach toward socialists and democracy to prevent the establishment of a left-wing dictatorship. Later, between 1922 and 1924, he distanced himself from the socialists, forming alliances with capitalist and anti-Marxist groups. Disillusioned with democracy, by 1927, Seipel advocated for replacing it with a clerical authoritarian system.

A dominant figure in Austrian politics during the 1920s, Seipel served as Chancellor from 31 May 1922 to 3 April 1929, except for a period between 1924 and 1926. In 1922, he managed to end severe inflation through an international stabilization loan, although this meant subjecting state economic policy to the supervision of the League of Nations. Deeply anti-socialist, he led a government coalition of Christian Socialists and Pan-Germans. Considered brilliant and the most capable conservative politician of his time, Seipel shared with his socialist rival, Otto Bauer, a firm commitment to defending their principles. Within his party, Seipel belonged to the most radical and conservative faction, which included the most capable leaders. Even when not leading the government, he wielded significant influence in the Christian Social Party. He played a crucial role in both the Christian Socialists' acceptance of the republic and their eventual abandonment of democracy. In his later years, Seipel supported constitutional reforms to establish an authoritarian government and worked closely with fascist groups like the Heimwehr (Home Guard), an organization similar to the German Freikorps. He died in 1932, suffering from diabetes and tuberculosis.

The son of a Viennese carriage driver, Seipel graduated from an academic high school (Staatsgymnasium) in Vienna in 1895, then studied Catholic theology at the University of Vienna. He was ordained a priest on 23 July 1899 and received his doctorate in theology in 1903. Seipel was a member or honorary member of numerous Catholic student fraternities.

In his 1907 work reflecting Catholic social teaching, Ethical Teachings on Economics of the Church Fathers, he was the first to use the phrase "economic ethics". In 1908 he joined the Catholic Theological Faculty of the University of Vienna. From 1909 to 1917 he was professor of moral theology at the University of Salzburg. There he published his study Nation and State (1916), which helped cement his later prominent role in the Christian Social Party. In the book he viewed the state – the self-governing political entity – as the primary justification of sovereignty, rather than the nation – a group that shares a common culture, as for example speakers of German. In 1917 he was appointed professor at the University of Vienna, succeeding the moral theologian Franz Martin Schindler.

On 27 October 1918, during the final days of the Austro-Hungarian Empire, Emperor Karl I appointed Seipel Minister of Public Works and Social Welfare in the ministry of Heinrich Lammasch, the last "imperial and royal" government of the Empire. At the beginning of November 1918, Seipel handed over his official duties to the government of Karl Renner of the Social Democratic Party of Austria. It had been appointed on 30 October 1918 by the State Council of German-Austria, the executive body of the short-lived Republic of German-Austria. The Lammasch ministry remained formally in office at the request of the Emperor until his own withdrawal. While still an imperial minister, Seipel was involved in formulating the declaration of abdication that the Emperor signed on 11 November 1918. On the same day the Emperor dismissed the Lammasch ministry.

On 16 February 1919 Seipel was elected on the Christian Social ticket to the Constituent National Assembly, the body that adopted the constitution for the First Austrian Republic, which replaced the Republic of German-Austria. Seipel's parliamentary group elected him to the club presidium, one of its leadership bodies.