| Native Name: | |
| Conventional Long Name: | Bishopric of Toul |
| Subdivision: | Prince-bishopric |
| Nation: | Holy Roman Empire |
| Era: | Middle Ages |
| Year Start: | 1048 |
| Year End: | 1648 |
| Event Pre: | Bishopric established |
| Date Pre: | 365 |
| Event Start: | Acquired territory |
| Event End: | Three Bishoprics annexed by France |
| Date End: | 1552 |
| Event Post: | Treaty of Westphalia recognises annexation |
| Date Post: | 1648 |
| P1: | Duchy of Lorraine |
| S1: | Three Bishoprics |
| Capital: | Toul |
| Image Map Caption: | The Three Bishoprics of Verdun, Metz and Toul |
The Diocese of Toul was a Roman Catholic diocese seated at Toul in present-day France. It existed from 365 until 1802. From 1048 until 1552 (de jure until 1648), it was also a state of the Holy Roman Empire.
The diocese was erected in 338 AD by St. Mansuetus. The diocese was a suffragan of the ecclesiastical province of Trier. In 550 AD, the Frankish Council of Toul was held in the city.
By the high Middle Ages, the diocese was located at the western edge of the Holy Roman Empire; it was bordered by France, the Duchy of Bar, and the Duchy of Lorraine. In 1048 it become a state of the Empire while that city of Toul itself became a Free Imperial City.
In 1552, both states were annexed by King Henry II of France; the annexations were formally recognized by the Empire in 1648 by the Peace of Westphalia. By then, they were part of the French province of the Three Bishoprics.
In 1766, the Duchy of Lorraine became part of France. In 1777 and 1778, territory was carved out of Toul to form two new dioceses: Saint Dié and Nancy, both of them suffragans of Trier. By the terms of the Concordat of 1802, Toul was suppressed. Its territory was merged with that of Nancy to form a new diocese — the Diocese of Nancy-Toul with it seat in Nancy. The geographic remit included three Departments of France: Meurthe, Meuse, and Vosges.