The Landing Craft, Support (Large) were two distinct classes of amphibious warfare vessels used by the United States Navy (USN) in the Pacific and the Royal Navy in World War II. The USN versions, which were later reclassified Landing Ship Support, Large, also performed radar picket duty and fire fighting.

A radar picket is a radar-equipped station, ship, submarine, aircraft, or vehicle used to increase the radar detection range around a nation or military force to protect it from surprise attack, typically air attack, or from criminal activities such as smuggling. By definition a radar picket must be some distance removed from the anticipated targets to be capable of providing early warning. Often several detached radar units would be placed in a ring to encircle a target to provide increased cover in all directions; another approach is to position units to form a barrier line.