William L. Kruer (born 20 April 1942, Louisville, Kentucky) is an American physicist, specializing in plasma physics.^[1]

Kruer studied at the University of Louisville (Master's degree, 1965) and received his Ph.D. in 1969 from Princeton University. Afterwards, he was a research associate scientist at the Princeton Plasma Physics Laboratory and from 1970 a full member of the research staff. Starting in 1972, he was a group leader for theoretical plasma physics and simulation at Lawrence Livermore National Laboratory and from 1993 a chief scientist in plasma physics there. He wrote an important book on laser plasma interactions.^[2]

In 1990, he received the James Clerk Maxwell Prize for Plasma Physics.^[3]