James "Jim" U. Lemke (December 26, 1929 - February 22, 2019) was an American physicist and entrepreneur who lived in San Diego.

He joined T.E.M.C.O, working on high-speed teletype encryption devices before moving to AV Manufacturing Company in New York as the vice-president of engineering, developing multi-track instrumentation recorders.

[12] Four years later, in 1982, Lemke was pivotal in establishing the Center for Magnetic Recording Research (CMRR) at UC San Diego.

Lemke obtained corporate donations for a new building for the center and could secure funding for four endowed professorships and for scientific equipment.

In 2004, Lemke founded Achates Power[15] to pursue the development of the two-cycle, opposed-piston internal combustion engine.

In 1981, in Ted Gildred's recreation of his father's 1942 flight from San Diego to Quito, Ecuador, Lemke flew as the safety "chaser" in his twin-engined Beech Baron.