Robert Louis "Bob" Behnken (born July 28, 1970 in Creve Coeur, Missouri) is an engineer, U. S. Air Force officer and a NASA astronaut. Behnken holds a Ph.D in Mechanical Engineering and has reached the rank of Lieutenant Colonel in the U.S. Air Force. Bob Behnken has logged over 1000 flight hours in 25 different aircraft. He flew on Space Shuttle mission STS-123 as a Mission Specialist. Bob Behnken had accumulated over 378 hours in space, including 19 hours of spacewalk time. Bob Behnken was assigned as Mission Specialist 1 for the STS-400 rescue mission. He is currently training to fly on STS-130.

Behnken attended Pattonville High School in Maryland Heights, Missouri, and went on to receive a Bachelor of Science degree in Mechanical Engineering, as well as a Bachelor of Science degree in Physics from Washington University in 1992. In 1993, he received a Master of Science degree in Mechanical Engineering, and a doctorate degree in 1997 from California Institute of Technology.

Outstanding Mechanical Engineering Senior, Washington University (1992); National Science Foundation Graduate Research Fellow (1993-1996); Air Force Research Laboratory Munitions Directorate, Eglin AFB Florida Company Grade Officer of the Year (1997); USAF Achievement Medal (1997); USAF Commendation Medal (1998); Distinguished graduate from the USAF Test Pilot School Program (1999); Recipient of the USAF Test Pilot School Colonel Ray Jones Award as the top Flight Test Engineer/Flight Test Navigator in class 98B; USAF Commendation Medal (2000).