The Delta 1000 series was an American expendable launch system which was used to conduct eight orbital launches between 1972 and 1975. It was a member of the Delta family of rockets. Several variants existed, differentiated by a four digit numerical code.

The same first stage and boosters were used on all variants. The first stage was an Extended Long Tank Thor, a further stretched version of the Long Tank Thor used on earlier versions, itself derived from the Thor missile. Four, six or nine Castor-2 solid rocket boosters were attached to increase thrust at lift-off.

Two different second stages were flown, depending on the variant. The Delta F was flown on three launches, with Explorer 47, 50 and 51, whilst other flights used a new variant, the Delta P. Some flights used a third stage, either the Star-37D or 37E, for launches beyond low Earth orbit.

Delta 1000 rockets were launched from Space Launch Complex 2W at Vandenberg AFB and Launch Complex 17B at Cape Canaveral. All eight launches were successful