The Delta 3000 series was an American expendable launch system which was used to conduct thirty five orbital launches between 1975 and 1989. It was a member of the Delta family of rockets. Several variants existed, which were differentiated by a four digit numerical code.

The first stage was the RS-27 powered Extended Long Tank Thor, first flown on the 2000-series. Three or nine Castor-4 solid rocket boosters were attached to increase thrust at lift-off, replacing the less powerful Castor-2 boosters used on earlier models. Two second stages were available; the Delta P, which had been flown on several older variants, or the Delta-K, an uprated version. Some launches used a three-stage configuration in order to reach higher orbits. A Star-37D, Star-37E, or Star-48B PAM-D could be used as an upper stage. Launches with PAM-D upper stages were designated Delta 3XX0 PAM-D, rather than assigning a code to the upper stage for use in the four-digit sequence. From the 4000-series onwards, the PAM-D received the upper stage code "5", however this was not applied retrospectively to 3000-series rockets, which were still in service at the time.

The Delta 3000 was launched from Space Launch Complex 2W at Vandenberg AFB and Launch Complex 17A and B at Cape Canaveral. Of the thirty five launches, two failed, and one resulted in a partial failure. The failures resulted in the loss of the Orbital Test Satellite, when an SRM malfunction caused the rocket to explode, and GOES-G due to an electrical fault which shut down the first stage engine. The partial failure was due to the premature cutoff of the first stage, which left the Dynamics Explorer spacecraft in a lower orbit than planned.

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