Kjell Norwood Lindgren (Chinese: 林其兒; pinyin: Lín Qí'ér; born January 23, 1973) is an American astronaut who was selected in June 2009 as a member of the NASA Astronaut Group 20. He launched to the International Space Station (ISS) as part of Expedition 44/45 on July 22, 2015.

Lindgren was born in Taipei, Taiwan, in 1973 to a Taiwanese mother and American father in the US Air Force; his Chinese name is Lin Qi'er (Chinese: 林其兒; pinyin: Lín Qí'ér). His family later moved to the Midwestern United States, but he spent most of his childhood in England. He attended Lakenheath American High School for a year before moving back to the United States, where he graduated from James W. Robinson Secondary School in Fairfax, Virginia in 1991.

After entering the United States Air Force Academy, he joined the Air Force Parachuting Team. In 1995, he received a Bachelor of Science (BS) degree in biology with a minor in Mandarin Chinese from the Air Force Academy. In 1996, he received a Master of Science (MS) degree in cardiovascular physiology from Colorado State University (CSU), in part for his work completing cardiovascular countermeasure research at NASA's Space Physiology Lab. He subsequently obtained a Doctorate of Medicine (MD) from the University of Colorado in 2002, and went on to complete a three-year residency in emergency medicine at Hennepin County Medical Center in Minneapolis. In 2006, he completed a post-doctoral fellowship and a Master of Health Informatics (MHI) at the University of Minnesota. He also completed a Master of Public Health (MPH) at the University of Texas Medical Branch in 2007 and a residency in aerospace medicine in 2008.

He began working for NASA at the Johnson Space Center in 2007. He went on to support ISS training operation at Star City, Russia and became the deputy crew surgeon for STS-130 and Expedition 24.

In June 2009, he was one of nine astronaut candidates selected by NASA out of 3500 applications and began training as part of NASA Astronaut Group 20. The nine Americans, as well as two Canadian Space Agency candidates and three JAXA candidates, started training at the Johnson Space Center in August 2009. The 14 candidates carried trained in various different fields including T-38 flight training, Extravehicular activity training, survival, International Space Station operations and other various skills. The group completed their training and Lindgren and his 13 classmates became eligible for future flight assignments on November 4, 2011.

In between finishing training, he worked in the Spacecraft Communicator and Extravehicular Activity branches of NASA, and he was the Spacecraft Communicator lead for Expedition 30.

From June 18, 2017, to June 27, 2017, Lindgren was commander of the NEEMO 22 mission to the Aquarius Reef Base, located 19 meters underwater off the coast of Florida. The NEEMO 22 mission focused on both exploration spacewalks and objectives related to the International Space Station and deep space missions. As an analogue for future planetary science concepts and strategies, the mission's crew also performed marine science under the guidance of Florida International University's marine science department. Objectives for the crew also included testing spaceflight countermeasure equipment, technology for precisely tracking equipment in habitat and studies of body composition and sleep. The crew also assessed hardware sponsored by ESA that will help crew members evacuate someone who has been injured on a future lunar spacewalk.

In 2013, he began training at the Gagarin Space Center and was assigned as backup flight engineer for Expedition 42/43 which launched on Soyuz TMA-15M. He was later assigned to Expedition 44/45 as a flight engineer. On July 22, 2015, Lindgren launched on his first mission to the ISS alongside Russian cosmonaut Oleg Kononenko and Japanese astronaut Kimiya Yui onboard Soyuz TMA-17M. Six hours later the trio docked to the ISS, officially joining Expedition 44 alongside Soyuz TMA-16M crewmembers Gennady Padalka and Mikhail Kornienko of Roscosmos and Scott Kelly of NASA. In November 2015, while on the ISS, Kjell played a set of bagpipes manufactured by McCallum Bagpipes Ltd as a memorial to Victor Hurst, who died in October of that year. McCallum Bagpipes was chosen to manufacture the bagpipes because they make them in plastic, which is easily sanitized and transported, ideal for space exploration. This is thought to be the first time the Great Highland bagpipes have been played in space.