The BOR-4 (БОР-4 Russian: Беспилотный Орбитальный Ракетоплан 4, Bespilotnyi Orbital'nyi Raketoplan 4, "Unpiloted Orbital Rocketplane 4") flight vehicle is a scaled (1:2) prototype of the Soviet Spiral VTHL (vertical takeoff, horizontal landing) spaceplane.

An uncrewed, subscale spacecraft, its purpose was to test the heatshield tiles and reinforced carbon-carbon for the Buran space shuttle, then under development.

[2] After reentry, they were designed to parachute to an ocean splashdown for recovery by the Soviet Navy.

On 16 March 1983[3]: 207  a Royal Australian Air Force P-3 Orion reconnaissance aircraft captured the first Western images of the craft as it was recovered by a Soviet ship near the Cocos Islands.

[4] Seven BOR were built, and four confirmed flights took place between 1982 and 1984.