Joseph Anton Blatter (also known in French as Joseph-Antoine Blatter; 8 March 1745 — 19 March 1807) was a Swiss prelate and the 73rd and last Prince-bishop of the Diocese of Sion, in the Republic of the Seven Tithings, in the modern Canton of Valais, from 1790 to 1799, and after the French invasion and dissolution of the republic, Bishop of Sion until his death in 1807.

In 1634, after decades of decreasing political influence of the bishopric over the Valais, the prince-bishop of Sion, Hildebrand II Jost, renounced the temporal power exercised by the office,[1] putting an end to a period of church rule in Valais that had started in 999,[2] and marking the official establishment of the (already existent de facto) Republic of the Seven Tithings.

[5] Two years prior to his election, in 1788, a great fire had swept through Sion, destroying most of the city, including the residence of the prince-bishop, the Château de Tourbillon.

Although Blatter by 1793 had plans to rebuild it, the politic upheavals and later the French invasion ended any possibility for such project[6] In the period from 1792 to 1794 he gave asylum to many clergy and lay people fleeing from the Reign of Terror in France, including a Trappist and a Poor Clare convent.

Following the crushing of the last revolt in the Upper Valais against the French troops in the Battle of Finges, in May 1799, Blatter went into exile in Novara for months.