Luna E-6 No.3, also identified as No.2 and sometimes by NASA as Luna 1963B,^[1] was a Soviet spacecraft which was lost in a launch failure in 1963. It was a 1,422-kilogram (3,135 lb) Luna E-6 spacecraft,^[2] the second of twelve to be launched,^[3] and the second consecutive launch failure.^[3] It was intended to be the first spacecraft to perform a soft landing on the Moon, a goal which would eventually be accomplished by the final E-6 spacecraft, Luna 9.

Luna E-6 No.3 was launched at 09:26:14 UTC on 3 February 1963, atop a Molniya-L 8K78L carrier rocket,^[3] flying from Site 1/5 at the Baikonur Cosmodrome.^[4] A torque sensor in the gyroscope used to control the pitch of the upper stage malfunctioned, resulting in control of the rocket being lost.^[5] The spacecraft failed to achieve orbit, and reentered the atmosphere over the Pacific Ocean.^[5] Prior to the release of information about its mission, NASA correctly identified that it had been an attempt to land a spacecraft on the Moon. However, they believed the launch had occurred on 2 February.^[1]