Christopher John "Chris" Cassidy is a retired NASA astronaut and United States Navy SEAL. Chris Cassidy achieved the rank of captain in the U.S. Navy. His first spaceflight was on a Space Shuttle mission in 2009. He was the Chief of the Astronaut Office at NASA from July 2015 until June 2017.

The Chief of the Astronaut Office is the most senior leadership position for active astronauts at the National Aeronautics and Space Administration (NASA). The Chief Astronaut serves as head of the NASA Astronaut Corps and is the principal advisor to the NASA Administrator on astronaut training and operations. The Chief's responsibilities include managing Astronaut Office resources and operations and helping to develop operating concepts and assignments for astronaut flight crew.