Savo Island is a minor island in the Solomon Islands group in the South Pacific ocean. It is located to the north-east of the northern tip of Guadalcanal Island. A high, round volcanic island, it is most well known as the location of five of the seven great naval battles fought in the Guadalcanal area during World War II, between the forces of the United States Navy (USN) and the Imperial Japanese Navy (IJN). The battles fought near Savo in the period 1942-1943 were initially called the "First Battle of Savo Island", the "Second Battle...", through the Fifth. These were subsequently renamed for the specific localities in the area where the battles were fought. There were so many warships sunk in these battles that the large sound bounded by Savo, Guadalcanal and Florida Islands was renamed Ironbottom Sound.

In most of these battles, the USN did not do well against the IJN. Prior to the First Battle of Savo Island there was a racist belief within the USN that the Japanese had poor eyesight and would not do well in night naval fighting. As a consequence, the USN had not practiced night fighting while the IJN had, and was well prepared with both training and superior equipment in some areas, such as torpedoes. This first battle on August 9th, 1942 was a disaster for the USN, with the loss of the cruisers Canberra, Vicennes, Quincy, and Astoria. Yet even this defeat of the USN showed that they were a genuine threat to following troopships carrying Imperial Japanese Army reenforcements to Guadalcanal - they were turned back, which greatly assisted the US Marine forces on the island.

This defeat at this battle, one of the worst in USN history, caused the USN Admiral (Scott) to emphasize readiness for night fighting, with all hands on night watch.

Following a draw in the Battle of the Eastern Solomons on August 24th and 25th, the training paid off in the Second Battle of Savo Island (now called the Battle of Cape Esperance) on October 11th and 12th of 1942. In this battle, the USN had the advantage of radar and a fortuitous position, having incidentally "crossed the T" of the IJN units. This, combined with a reversal of direction that allowed two passes against their enemy, resulted in the sinking the IJN warships Fubuki and Furutaka and is considered a substantal victory for the USN in this battle. This victory came at a critical time for the US forces, greatly boosting moral both in the Pacific Theater and on the Home Front.

Subsequent naval battles in the Guadalcanal actions were not as good for the USN, but like many other engagements in the first years of this war, the tactical draws and defeats for the U.S. forces in this location would ultimately result a strategic victory - the forces of the Japanese Empire were to be worn away and defeated by the military and industrial power of the USA, with the Japanese abandoning their positions in the southern Solomons.

For an index to the various naval battles in the larger region see Battle of Guadalcanal

For an earlier tactical draw that is also considered a strategic victory, see the Battle of the Coral Sea. This battle set the southeastern limits of Japanese hegemony in the Pacific, preventing further Japanese advancement to the south shores of New Guinea, from where they would threaten Australia, and then enter the Indian Ocean, where they could operate effectively against allied forces in southern China, Burma, and India.