Claude Nicollier (born 2 September 1944) is the first astronaut from Switzerland. He has flown on four Space Shuttle missions. His first spaceflight (STS-46) was in 1992, and his final spaceflight (STS-103) was in 1999. He took part in two servicing missions to the Hubble Space Telescope (called STS-61 and STS-103). During his final spaceflight he participated in a spacewalk, becoming the first European Space Agency astronaut to do so during a Space Shuttle mission (previous ESA astronauts conducted spacewalks aboard Mir, see List of spacewalks and moonwalks 1965–1999). In 2000 he was assigned to the Astronaut Office Extravehicular Activity Branch, while maintaining a position as Lead ESA Astronaut in Houston. Nicollier retired from ESA in April 2007.

He was appointed full professor of Spatial Technology at the École Polytechnique Fédérale de Lausanne on 28 March 2007.

He was an expert board member of Swiss Space Systems, until the company's dissolution.

Nicollier was born September 2, 1944. After graduating from the Gymnase de la Cité (high school) in Lausanne in 1962, he studied physics at the University of Lausanne and received a Licentiate degree in 1970. He then worked as a graduate scientist from 1970 to 1973 at the Institute of Astronomy at the university and at the Geneva Observatory, before obtaining a post Diploma degree in astrophysics from the University of Geneva in 1975. In parallel, he became a Swiss Air Force pilot in 1966, in the Fliegerstaffel 5 on Hawker Hunter where he holds a commission as captain, and has logged 5,600 hours flying time, including 4,000 hours in jet aircraft. Later, in 1988, he graduated as a test pilot from the Empire Test Pilot's School in Boscombe Down, United Kingdom.

In 2004, he started teaching at the École Polytechnique Fédérale de Lausanne, and became a full professor in March 2007.

Concurrently with his part-time research activities, he joined the Swiss Air Transport School in Zürich and became an airline pilot in 1974, assigned as a DC-9 pilot for Swissair. At the end of 1976, he accepted a Fellowship at the European Space Agency’s (ESA) Space Science Department at Noordwijk, Netherlands, where he worked as a research scientist in various airborne infrared astronomy programs. In July 1978, he was selected by ESA as a member of the first group of European astronauts. Under agreement between ESA and NASA, he joined NASA Astronaut Group 9 selected in May 1980 for astronaut training as a mission specialist. Unlike colleague Wubbo Ockels—who withdrew from training to focus on Spacelab and remained an ESA payload specialist—Nicollier became a mission specialist, the first non-American to become a full-time NASA astronaut.

Nicollier's technical assignments in the Astronaut Office have included flight software verification in the Shuttle Avionics Integration Laboratory (SAIL), participation in the development of retrieval techniques for the Tethered Satellite System (TSS), Remote Manipulator System (RMS), and International Space Station (ISS) robotics support. From the spring of 1996 to the end of 1998, he was head of the Astronaut Office Robotics Branch. From the year 2000 on, he was assigned to the Astronaut Office EVA (Extravehicular Activity) Branch, while maintaining a position as Lead ESA astronaut in Houston. Nicollier retired from ESA in April 2007.

He is a member of the Swiss Astronomical Society, the Astronomical Society of the Pacific, the Swiss Air Force Officers Society (AVIA), and the Swiss Academy of Engineering Sciences and fellow of the British Interplanetary Society. He is also an honorary member of the Swiss Aero Club, the Swiss Society of Engineers and Architects, and the Swiss Astronomy Day Society.