The naval war on Lake Constance (German: Seekrieg auf dem Bodensee) was a series of conflicts that took place on Lake Constance, beginning in 1632, in the context of the Thirty Years' War (1618 to 1648). At that time various powers ruled different parts of the shoreline: in the north and east was Roman Catholic, Habsburg Anterior Austria; in the northwest and west the troops of the Protestant Duchy of Württemberg with their allies from Kingdom of Sweden and Kingdom of France. These various powers sought, for strategic reasons, to exercise their hegemony over the area of Lake Constance. Only the partly Catholic and partly Protestant southern shore which belonged to the Old Swiss Confederacy maintained an uneasy neutrality due to their divided loyalties.
The changing course of this post-war period of the Thirty Years' War brought no clear success to either party. The Protestant side (reinforced by France) could not seriously threaten imperial possessions; the Imperialists succeeded in maintaining their positions on the whole and to inflict telling losses on their enemy. Swedish/Württemberg naval domination in the last two years of the war had no wide-reaching significance by that stage.