The Atlas SLV-3 or SLV-3 Atlas was an American expendable launch system derived from the SM-65 Atlas / SM-65D Atlas missile. Most space launcher variants of the Atlas up to 1965 were derived from the D-series Atlas ICBM with custom modifications for the needs of the particular mission. The SLV-3 would use a standardized configuration based on the Atlas D missile for all launches with the exception of different widths for the top of the rocket depending on the upper stage being flown.

The SLV-3 had thicker gauge tank walls to support the weight of upper stages as well as upgraded engines and removal of unneeded ICBM hardware such as retrorockets. Although the main engines had greater thrust, the verniers were detuned slightly in the interest of improved ISP (vacuum specific impulse).