Yi So-yeon (born June 2, 1978) is a biotechnologist and astronaut who became the first Koreans to fly in space. Upon return from her mission aboard the ISS, Yi continued as a KARI researcher, attending the International Space University before retiring from the agency to pursue an MBA at the University of California, Berkeley Haas School of Business and joining commercial astronaut corps the Association of Spaceflight Professionals.
Yi So-yeon was born to father Yi Gil-soo and mother Jeong Geum-soon and raised in Gwangju, South Korea. She studied at Gwangju Science High School. She earned bachelor's and master's degrees with a focus on mechanics at KAIST in Daejeon. Her doctorate in biotech systems was conferred on 29 February 2008 in a ceremony at KAIST, although she was unable to be present due to her training commitments in Russia. In 2010, she enrolled in the MBA program at the Haas School of Business at the University of California, Berkeley  In 2015 she taught at Everett Community College in Washington State as a Engineering Physics Professor. 
Yi was one of the two finalists chosen on 25 December 2006 through the Korean Astronaut Program. On 5 September 2007, the Korean Ministry of Science and Technology chose Ko San, over Yi So-yeon, following performance and other tests during their training in Russia.
On 7 March 2008, she was selected to train with the primary crew, and on 10 March the Ministry of Education, Science and Technology announced that Yi would replace Ko. This was after the Russian Federal Space Agency asked for a replacement because Ko violated regulations several times at a Russian training center by removing sensitive reading materials and mailing one back to Korea.
On 8 April 2008, Yi was launched into space on board Soyuz TMA-12, with two Russian cosmonauts. South Korea is reported to have paid Russia $20M for Yi's space flight. She is the third woman, after Helen Sharman of the United Kingdom and Anousheh Ansari an Iranian American, to be the first national from their country in space.
Flying as a guest of the Russian government through a commercial agreement with South Korea, Yi's role aboard Soyuz and the ISS is referred to as a spaceflight participant (Russian: uchastnik kosmicheskovo poleta) in Russian Federal Space Agency and NASA documents and press briefings.
During her mission, Yi So-yeon carried out eighteen science experiments for KARI and conducted interviews and discussions with media. In particular, she took with her 1,000 fruit flies in a special air-conditioned container box (Konkuk University experiment). She monitored the way the changes in gravity and other environmental conditions alter the behaviour of the flies, or their genome.
Other experiments involved the growth of plants in space, the study of the behaviour of her heart, and the effects of gravity change on the pressure in her eye and shape of her face. With a specially designed three-dimensional Samsung camera, Yi took six shots of her face every day to see how it swells in the different gravity. She also observed the Earth, and in particular the movement of dust storms from China to Korea. She also measured the noise levels on board the ISS.
At the end of the mission, Yi returned to Earth along with ISS crew members Peggy Whitson and Yuri Malenchenko aboard Soyuz TMA-11, on April 19, 2008. Due to a malfunction with the Soyuz vehicle, the craft followed a ballistic re-entry, which subjected the crew to severe gravitational forces, up to ten times the amount experienced on Earth.
As a result of the re-entry, the TMA-11 craft used in the return flight landed 260 miles (420 km) off-course from its target in Kazakhstan. All three survived, although requiring observation by medical personnel. Yi was hospitalized after her return to Korea due to severe back pains. Though many believed these pains were the result of the rough landing, they were in fact normal and expected. They were the result of spinal re-compression.
After her flight, Yi worked as a researcher at KARI and as Korea's space ambassador with Ko San. She was to receive income from future TV commercials. On October 4, 2008, Yi launched the International Institute of Space Commerce at a ceremony held in Douglas, Isle of Man.
In 2009, Yi became the first astronaut to attend the International Space University (ISU) Space Studies Program (SSP) at NASA Ames Research Center, held in conjunction with the inaugural class of the Singularity University (SU) Graduate Studies Program (GSP).
On August 13, 2014, the Korean Aerospace Research Institute announced that Yi had resigned for personal reasons, ending the South Korean space program. In the interview, she gave two reasons as to why she resigned from the program: first, she was preparing to marry a Korean-American man; second, she wanted to study for an MBA at UC Berkeley.
Association of Spaceflight Professionals
Following her graduation from the University of California, Berkeley Haas School of Business, Yi joined the Association of Spaceflight Professionals, the world's first commercial astronaut corps, and serves on its Board of Directors.
- Association of Spaceflight Professionals
- Christopher Altman
- Commercial astronaut
- Erik Seedhouse
- Korean Astronaut Program
- Korea Aerospace Research Institute
- Private spaceflight
- Timeline of space travel by nationality
- ARISS: Amateur Radio on the International Space Station