Leroy Chiao (Chinese: 焦立中; born August 28, 1960) is an American chemical engineer, retired NASA astronaut, entrepreneur, motivational speaker, and engineering consultant. Chiao flew on three Space Shuttle flights, and was the commander of Expedition 10, where he lived on board the International Space Station from October 13, 2004 to April 24, 2005. He is also a co-author and researcher for the Advanced Diagnostic Ultrasound in Microgravity project.

Chiao was born to a Taiwanese American family in Milwaukee, Wisconsin. He was raised in Danville, California. His parents are Taiwanese waishengren who were born in Shandong province in mainland China but moved to Taiwan. They met while studying at a Taiwanese university in the 1950s before immigrating to the U.S.

Chiao graduated from Monte Vista High School in Danville in 1978. In 1983, he earned a Bachelor of Science in chemical engineering from the University of California, Berkeley. He later earned an Master of Science and a Doctor of Philosophy in chemical engineering from the University of California, Santa Barbara in 1985 and 1987, respectively.

Chiao's parents were chemical engineers who immigrated to Milwaukee from the Republic of China in the late 1950s for graduate school. Stressing a high doctorate-level science education, his parents encouraged him to follow their lead and become an engineer. Chiao's aviator call sign is "Shandong," the name of the Chinese province where his parents grew up.

Upon graduation, Chiao joined the Hexcel Corporation in Dublin, California from 1987 to 1989. He was involved in process, manufacturing, and engineering research on advanced aerospace materials, and worked on a joint NASA-JPL/Hexcel project to develop a practical, optically correct, precision segment reflector made entirely of advanced polymer composite materials for future space telescopes, as well as working on cure modeling and finite element analysis. In January 1989, Chiao joined the Lawrence Livermore National Laboratory in Livermore, California, where he was involved in processing research for the fabrication of filament-wound and thick-section aerospace composites. Chiao also developed and demonstrated a mechanistic cure model for graphite fiber and epoxy composite material (see Graphite-reinforced plastic). An instrument-rated pilot, Chiao has logged over 3300 flight hours in a variety of aircraft.

At age 29, Chiao was selected by NASA in January 1990 (the youngest in Group 13) and became an astronaut in July 1991. He qualified for flight assignment as a mission specialist. His technical assignments included: Space Shuttle flight software verification in the Shuttle Avionics Integration Laboratory (SAIL); crew equipment, Spacelab, Spacehab, and payload issues for the Astronaut Office Mission Development Branch; training and flight data file issues; and extravehicular activity (EVA) issues for the EVA Branch. Chiao is Chief of the Astronaut Office EVA Branch.

A veteran of four space flights, Chiao flew as a mission specialist on STS-65 in 1994, STS-72 in 1996 and STS-92 in 2000. Chiao had logged over 36 days and 12.5 hours in space, including over 26 EVA hours in four spacewalks, before his mission aboard the International Space Station.

Chiao is fluent in Mandarin Chinese. Additionally, Chiao also learned Russian to communicate with Russian cosmonauts as part of the International Space Station program. On November 2, 2004, Chiao voted in the 2004 United States presidential election while aboard the International Space Station, making him the first American to vote in a presidential election while in space. McDonald's presented Chiao with a Big Mac and French fries at their branch in Star City as one of his first meals since returning to Earth after his ISS assignment. Among the souvenirs he brought into space in his previous space flights were a Chinese flag and a quartz-carved rose from Hong Kong.