The Schmalkaldic League is a defensive alliance of Lutheran princes within the Holy Roman Empire during the mid-sixteenth century.

Although originally started for religious motives soon after the start of the Protestant Reformation, its members eventually intend for the League to replace the Holy Roman Empire as their source of political allegiance.

While it is not the first alliance of its kind, unlike previous formations, such as the League of Torgau, the Schmalkaldic League has a substantial military to defend its political and religious interests.

It receives its name from the town of Schmalkalden, in the German state of Thuringia.