Dawn is a NASA spacecraft tasked with the exploration and study of the asteroid Vesta and the dwarf planet Ceres, the two largest members of the asteroid belt. The spacecraft was constructed with some European cooperation, with components contributed by partners in Germany, Italy, and the Netherlands. The Dawn mission is managed by NASA's Jet Propulsion Laboratory.

Dawn will be the first spacecraft to visit either Vesta or Ceres. It may furthermore be the first spacecraft to orbit two separate extraterrestrial bodies, using ion thrusters to travel between its targets. Previous multi-target missions using conventional drives, such as the Voyager program, were restricted to flybys.

Launched on September 27, 2007, Dawn entered orbit around Vesta on July 16, 2011, and will explore it until August 26, 2012. Thereafter, the spacecraft will head to Ceres, which it is scheduled to reach in February 2015.Dawn is NASA’s first purely exploratory mission to use ion propulsion.

The status of the Dawn mission has changed several times. In December 2003, the project was first cancelled, and then reinstated in February 2004. In October 2005, work on Dawn was placed in "stand down" mode. In January 2006, Dawn's "stand down" was discussed in the press as "indefinitely postponed", even though NASA had announced no new decisions regarding the mission's status. On March 2, 2006, Dawn was cancelled by NASA.