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, it was also a state of the Holy Roman Empire.

The Three Bishoprics constituted a government of the Kingdom of France consisting of the dioceses of Metz, Verdun, and Toul within the Lorraine region. The three dioceses had been Prince-bishoprics of the Holy Roman Empire until they were seized by King Henry II of France between April and June 1552. At the end of the Thirty Years' War, they were officially ceded to France by the 1648 Peace of Westphalia.