The Marine Corps Early Warning Detachment, Guadalcanal (1942–43) was a ground based early-warning radar detachment that provided long range detection and rudimentary fighter direction against Japanese air raids during the Battle of Guadalcanal. Initially deployed as part of the headquarters of Marine Aircraft Group 23, this detachment established an SCR-270 long range radar that allowed the Cactus Air Force to husband its critically short fighter assets during the early stages of the battle when control of the island was still very much in doubt. The detachment arrived on Guadalcanal on 28 August 1942, began operating in mid-September, and did not depart until early March 1943. Combat lessons learned from this detachment had a great deal of influence on the Marine Corps' development of its own organic, large scale air warning program which began in early 1943.

The SCR-270 was one of the first operational early-warning radars. It was the U.S. Army's primary long-distance radar throughout World War II and was deployed around the world. It is also known as the Pearl Harbor Radar, since it was an SCR-270 set that detected the incoming raid about 45 minutes before the December 7, 1941, attack on Pearl Harbor commenced.