Fred Weldon Leslie is an American scientist who flew on the NASA STS-73 Space Shuttle mission as a payload specialist.

After Leslie earned his Ph.D. in 1979, he served as a post doctoral research associate at Purdue University studying fluid vortex dynamics.

Since 1983, he has served as a co-investigator for the Geophysical Fluid Flow Cell experiment which examines spherical rotating convection relevant to the atmospheres of stars and planets.

Leslie was a principal investigator for the Fluid Interface and Bubble Experiment examining the behavior of a rotating free surface aboard NASA's KC-135 aircraft flying low-gravity trajectories.

Leslie also worked in the MSFC Neutral Buoyancy Simulator as a suited subject and safety diver supporting procedure tests for extra-vehicular activity.