The Battle of Abtao was a naval battle fought on February 7, 1866, during the Chincha Islands War, between a Spanish squadron and a combined Peruvian-Chilean fleet, at the island of Abtao in the Gulf of Ancud near Chiloé Archipelago in south-central Chile. It reduced to a long-range exchange of fire between the two squadrons, as the Allied ships, anchored behind the island, were protected by shallow waters impracticable for the Spanish ships, whose gunnery, nevertheless, proved more accurate and inflicted damage to the Chilean and Peruvian ships.