Foedus Cassianum

The Foedus Cassianum (/ˈfdəs ˌkæʃiˈnəm/ in English) or the Treaty of Cassius was, according to Roman tradition, a treaty which was made between the Roman Republic and the Latin League in 493 BC after the Battle of Lake Regillus. It ended the war between the Latin League and Rome, placing Rome as equal in power to all of the members of the League combined.

The treaty was significant in serving as a model for later treaties between Rome and other Italic polities, which evolved into the large system of protectorates which became known as socii.