Pluto Kuiper Express was an interplanetary space probe that was proposed by Jet Propulsion Laboratory (JPL) scientists and engineers and under development by NASA.

The spacecraft was successfully launched in January 2006, after a financial standoff with NASA and additional delays, and went on to perform the first ever flyby of the Pluto-Charon system in July 2015.

[5] NASA tried to negotiate with Russia for use of Proton rockets to launch the spacecraft, in exchange for carrying Russian "Drop Zond" probes to Pluto.

[6] Another idea, emanating from the Max Planck Institute, would have had Germany contribute funding for the launch, in exchange for Pluto Express carrying a German probe to be dropped at Io during the Jupiter gravity assist.

Scientific equipment on board would have included visible light imaging systems, infrared and ultraviolet spectrometers, and an ultrastable oscillator (USO) for use in a radio occultation experiment.

The spacecraft was to have been a simple hexagonal prism-shaped structure weighing some 220 kg (485 lb), powered by radioisotope thermal generators (RTGs) similar to those used on the Galileo and Cassini missions.

Early in the mission's planning there was suggestion of combining efforts with the Russian space agency and including Zond probes to study the Plutonian atmosphere.