| Designation | Date | Country | Event |
| Shenzhou 2 | January 9 | P.R. of China | Second uncrewed test flight & recovery, after 108 orbits, of an experimental manned capsule for use by "taikonauts", with a monkey, a dog, a rabbit and snails. |
| STS-98 (Atlantis) | February 7 | United States | ISS mission 5A with the $1.4-billion US Laboratory module Destiny. Docking at the station was on 2/9 and Lab installation at the Node on 2/10. |
| STS-102 (Discovery) | March 8 | United States | ISS mission 5A.1, first "crew rotation" flight, carrying Expedition 2 crew, resupply & science racks, in multi-purpose logistics module (MPLM) Leonardo (1st flight). |
| Mars Odyssey | April 7 | United States | Launch of the 2001 Mars probe Odyssey on a Delta-2 for a six-month, 286-million miles voyage to the Red Planet. Arrived successfully on October 24. |
| GSat 1 | April 18 | India | First launch of new GSLV rocket with Russian-built 3rd stage. Geosynchronous comsat GSat1 did not reach correct orbit due 3rd stage engine underperformance. |
| STS-100 (Endeavour) | April 19 | United States | ISS mission 6A, with the Canadian-built robotarm Canadarm2 and 2nd MPLM, Raffaello, on its 1st flight. The crane-like manipulator was installed on 4/22. |
| Soyuz TM-32/ISS 2S | April 28 | Russia | Launch of 1st "taxi flight" to ISS, bringing a "fresh" Soyuz crew return vehicle (CRV) and carrying the world's first paying "space tourist", U.S. businessman Dennis Tito. |
| MAP | June 30 | United States | NASA's Microwave Anisotropy Mission, launched on a Delta-2, to measure temperature fluctuations in the cosmic microwave background from L2 libration point. |
| STS-104 (Atlantis) | July 12 | United States | ISS mission 7A, carrying the Joint Airlock Quest, which was installed at the ISS Node on 7/14. Arrival of Quest marked end of ISS Phase 2, begin of Phase 3. |
| Artemis | July 12 | Europe | Launch of the 10th Ariane 5, with the technological comsat Artemis & broadcast satellite B-Sat2b. Both left in lower orbits as planned due to upper stage failure. |
| Genesis | August 8 | United States | Launch of interplanetary probe Genesis on a Delta-2 to the first Earth-Sun libration point L1 to collect samples of the solar wind and return them in September 2004. |
| STS-105 (Discovery) | August 10 | United States | ISS mission 7A.1, 2nd crew rotation, carrying Leonardo (2nd flight) and replacing Expedition 2 crew with Expedition 3. Also conducted two spacewalks. |
| DC-1/ISS 4R | September 14 | Russia | Launch of the Russian docking compartment DC-1 "Pirs" on a Soyuz-U. Installed at Service Module Zvezda on 9/16. This also added a 2nd airlock for spacewalks. |
| Soyuz TM-33/ISS 3S | October 21 | Russia | Launch of 2nd "taxi" flight to ISS, with new Soyuz CRV and a paying "guest" cosmonaut, researcher Claudie Haigneré from CNES/France. Returned on TM-32. |
| STS-108 (Endeavour) | December 5 | United States | ISS mission UF-1, 1st utilization flight to ISS, with MPLM Raffaello and 4th expeditionary crew, to "rotate" with Expedition 3 after its 128-days stay in space. |