The 'Battle of Blackett Strait' was a naval battle of the Pacific War fought between small US and Japanese forces in the Blackett Strait between Kolombangara and Arundel islands in the Solomon islands group (6 March 1943).

The battle resulted from a chance encounter between two Japanese destroyers involved in a resupply run to Vila, on the southern end of Kolombangara island,. and a US Navy force of three light cruisers and three destroyers which had been tasked with a bombardment of the Japanese shore facilities around Vila. The two forces clashed as the Japanese destroyers were withdrawing through the Kula Gulf. In the short battle that followed the two Japanese destroyers were sunk, after which the US ships completed their bombardment of.

After the US victory of February 1943 in the Guadalcanal campaign stemming from the ''Watchtower' landing of 7 August 1942, operations in the Solomon islands group shifted to the north-west, where the Japanese maintained a substantial garrison on Kolombangara, which is part of the New Georgia islands group. Air bases had been established at Munda, on the western coast of New Georgia, and at Vila on the southern coast of Kolombangara. Allied efforts to reduce these bases were initially undertaken by air attack, but later came to include naval bombardment in preparation for the the 'Toenails' amphibious assault, and subsequent land campaign, to take New Georgia from a time late in June 1943. Meanwhile, the Japanese continued to increase their strength on and around these bases as part of their efforts to reinforce the southern defences of their main base area around Rabaul on New Britain island.

On the night of 5 March 1943, the Japanese destroyers Murasame and Minegumo delivered supplies to the Japanese base at Vila on Kolombangara island. These ships constituted part of Captain Masao Tachibana’s 4^th Destroyer Squadron of Vice Admiral Nobutake Kondo’s 2^nd Fleet. The two destroyers' passage to Vila was undertaken through the Vella Gulf and Blackett Strait, and Tachibana decided to return to the Shortland islands via the shorter route through the Kula Gulf.

Operating from Efate, Rear Admiral Aaron S. Merrill’s Task Force 'Mike' (otherwise Task Force 68) comprised the three 'Cleveland' class light light cruisers Montpelier (flagship), Cleveland and Denver, and the three 'Fletcher' class destroyers Conway, Cony and Waller.

As they withdrew through the Kula Gulf after landing their cargo, the Japanese destroyers encountered TF68, which was on it way to bombard Japanese positions at Vila. Two US submarines, Grayback and Grampus, had been assigned to support Merrill’s force, and were stationed along likely routes for Japanese ships withdrawing from Kula Gulf. Merrill’s attack on Vila was timed to coincide with another attack on Munda by four destroyers under Captain Robert Briscoe.

The US force was steaming to the south-west about 2 miles (3.2 km) off the New Georgia coast at a speed of about 20 kt, and meanwhile the Japanese ships were heading in the opposite direction along the eastern coast of Kolombangara, to the north-east of Sasamboki island off Stanmore. First contact was established by US radar operators at about 00.57 on 6 March, and the US ships opened fire at 01.01. The US cruisers engaged to starboard with their 6-in (152-mm) guns at a range of some 11,000 yards (10060 m). Radar-controlled gunnery was still in its infancy and there was a tendency for the initial barrage to fall on the same, usually nearest, target. In earlier Pacific Ocean naval battles, this tactical deficiency had allowed the Japanese successfully to engage attacking US ships with torpedoes and had resulted in several losses for the US forces. In this case, the entire opening salvo straddled Murasame. As Minegumo's captain began passing orders to his crew, Murasame was hit by the sixth US salvo, which was soon followed by a salvo of five torpedoes fired by the destroyer Waller. At about 01.15, one of these torpedoes hit Murasame, which exploded, caught fire and eventually sank. The explosion was reportedly heard by Briscoe’s force about 25 miles (40 km) away around Munda. The US cruisers then rapidly shifted target, doing so before Minegumo could launch any torpedoes.

Minegumo meanwhile tried to return fire, aiming for the flashes of the US gun batteries off their starboard bow. After a few minutes, though, the second Japanese destroyer was also hit and began to sink. As the surviving Japanese crew abandoned ship, firing ceased at 01.14. After the engagement, the US vessels completed a turn to starboard when they were approximately due east of the Blackett Strait and north of Tunguirili Point. At 01.24, they commenced a northerly bombardment run off the Kolombangara coast, having been delayed by only 16 minutes. Under the direction of a spotter aeroplane, the US gunners targeted 'supply dumps, runways, bivouacs and dispersed aircraft' in a bombardment that was reportedly very accurate and therefore destructive. Several Japanese shore batteries responded, firing on the bombarding ships, but were knocked out quickly with counter-battery fire. After completing their task at 01.40, Merrill’s ships withdrew through the New Georgia Sound.

Some 174 Japanese sailors lost their lives during the battle: of these, 128 were from Murasame and the other 46 from Minegumo. The survivors swam to shore on Kolombangara: these survivors totalled 53 men from Murasame and 122 from Minegumo. Two other survivors from Minegumo were later captured by US forces. One of the US submarines assigned to support the operation, Grampus, went missing and did not return to base at the end of its patrol: the boat’s fate remains unknown and it is uncertain if it was lost as a result of actions during the Blackett Strait operation or before them. It was officially listed as missing presumed lost on or before 3 March although there is a possibility that the boat was attacked by Minegumo during the evening of 5/6 March.

On 20 March, the Allies began mining operations in the central part of the Solomon islands group using US Navy and US Marine Corps torpedo bombers to sow mines throughout the northern Solomon islands group. After a month, these operations were briefly suspended as a result of the Japanese 'I' as a result of the need to free aircraft of the Air Solomons command to respond in the event of further attacks. In May, these operations resumed. On 7 May, the US minelayers Gamble, Breese and Preble, escorted by the destroyer Radford, laid mines across Blackett Strait in an attempt to interdict Japanese ships traveling through this waterway. On the following day, the Japanese destroyers Oyashio, Kagero and Kuroshio all hit mines in that area. Kuroshio sank immediately, and Kagero and Oyashio sank later in that day after being attacked and further damaged by US aircraft from Henderson Field on Guadalcanal following a radio report from an Australian coastwatcher on Kolombangara.