Giotto was a European robotic spacecraft mission from the European Space Agency. The spacecraft flew by and studied Halley's Comet and in doing so became the first spacecraft to make close up observations of a comet. On 13 March 1986, the spacecraft succeeded in approaching Halley's nucleus at a distance of 596 kilometers. It was named after the Early Italian Renaissance painter Giotto di Bondone. He had observed Halley's Comet in 1301 and was inspired to depict it as the star of Bethlehem in his painting Adoration of the Magi in the Scrovegni Chapel.

Members of the ESA’s Solar System Working Group started investigating a mission to Halley’s comet in 1977 before rejecting it in August 1978 in favour of a lunar orbiter. Shortly afterwards this was reversed by the Science Advisory Committee and the ESA started to study a joint mission with NASA. This mission was to be the International Comet Mission consisting of a carrier NASA probe and smaller European probe based on the ISEE-2. The plan was for the American probe to release the European probe towards Halley for a close flyby before going on to explore Comet 10P/Tempel. The NASA probe was cancelled November 1979.

Proposals then moved to an Ariane 1 launched mission with the first option considered being one suggested by Giuseppe Colombo. Named HAPPEN it involved using parts for a planned Geos-3 satellite to first examine the earth's Magnetotail before flying through the tail of Halley’s comet in march 1986. This was rejected 24 January 1980 by the Solar System working group for not offering to return enough information on Halley. In February 1980 it was proposed that the Ariane 1 launch two Geos based probes. One to examine the magnetotail and the other to target Halley’s comet. It was at this point the name Giotto name started being used. The proposal was approved by the Science Advisory Committee and then moved onto the Science program committee. The Science program committee initially rejected the mission in favour of the Hipparcos satellite while giving Giotto at chance for a second submission without the Magnetotail mission but with more extensive planning and a budget of 80 million accounting units. In July 1980 the committee approved the second proposal with a budget of 80 million accounting units. The Hipparcos program, while delayed, also continued.

During March 1981 British Aerospace submitted its Geos based design to the ESA. This was rejected due to issues with power and temperature control. In the same period it was found that the Geos design had become outdated to the point where it was no longer possible to obtain parts. As a result a new and somewhat larger craft was designed although British Aerospace remained the primary contractor.

Originally it was planned to launch Giotto on an Ariane 2 along with a commercial satellite. This was then shifted to an Ariane 3 before difficulties with finding a customer who wanted to fly during the launch window resulted in Giotto being assigned solo to an Ariane 1 which was available after EXOSAT was launched by a Thor-Delta.

There were plans to have observation equipment on board a Space Shuttle in low-Earth orbit around the time of Giotto's fly-by, but they in turn fell through with the Challenger disaster.

The plan then became a cooperative armada of five space probes including Giotto, two from the Soviet Union's Vega program and two from Japan: the Sakigake and Suisei probes. The idea was for Japanese probes and the pre-existing American probe International Cometary Explorer to make long distance measurements, followed by the Soviet Vegas which would locate the nucleus, and the resulting information sent back would allow Giotto to precisely target very close to the nucleus. Because Giotto would pass so very close to the nucleus ESA was mostly convinced it would not survive the encounter due to the spacecraft colliding at very high speed with the many dust particles from the comet. The coordinated group of probes became known as the Halley Armada.

The cylindrical spacecraft was 1.87 m in diameter 2.85m long. It had and had three internal platforms. Built by British Aerospace in Filton, Bristol, it carried a dust shield (Whipple shield) as proposed by Fred Whipple. The shield comprised a thin (1 mm) aluminium sheet separated by a space and a thicker (12 mm) Kevlar sheet. The later Stardust spacecraft would use a similar Whipple shield. Giotto also had a 1.51 m diameter antenna that it used to communicate with Earth. The craft was painted white using an electively conductive paint developed by Centre national d'études spatiales.