Umberto Guidoni (born 18 August 1954 in Rome) is an Italian astrophysicist, science writer and a former ESA astronaut, being the first European to visit the International Space Station.

Guidoni trained as an alternate payload specialist for that mission and made his first spaceflight aboard the Space Shuttle Columbia STS-75 in 1996, which included the second flight of the TSS system (TSS-1R).

In September 2001, Guidoni was assigned to ESA's European Space Research and Technology Centre (ESTEC) as crew support for the payloads to be developed for the Columbus Laboratory.

He also proposed the amendment 16 to protect the freedom of the press from the strict application of the EU directive (IPRED2) on criminal measures aimed at ensuring the enforcement of intellectual property rights.

On 15 April 1996, Guidoni was appointed Commander of the Order of Merit of the Italian Republic[6] by Oscar Luigi Scalfaro, President of Italy.