Steven Weldon Squyres (born January 9, 1956) is an American geologist and planetary scientist.

He received the Harold C. Urey Prize from the Planetary Division of the American Astronomical Society in 1987.

From 1978 to 1981 he was an associate of the Voyager mission to Jupiter and Saturn, participating in analysis of imaging data.

In November 2011, NASA Administrator Charles Bolden named Squyres chairman of the NAC, succeeding Kenneth Ford, the founder and director of the Florida Institute for Human and Machine Cognition.

[14] On September 19, 2011, NASA announced that Squyres would serve as an aquanaut aboard the Aquarius underwater laboratory during the NEEMO 15 undersea exploration mission from October 17–30, 2011.

[16][17] On the afternoon of October 21, Squyres and his crewmates officially became aquanauts, having spent over 24 hours underwater.

[16] Squyres commented in a post-NEEMO 15 interview, "I would love to continue to be part of NEEMO - in any capacity.