John Holmes Malmberg (July 5, 1927 – November 1, 1992) was an American plasma physicist and a professor at the University of California, San Diego.

From 1957 to 1969, he was a staff scientist working in the area of plasma physics at General Atomics in San Diego, California.

In an era when small-scale and basic plasma physics research was nearing an ebb, Malmberg emphasized the importance of being able to follow the internal logic of the science, which he believed to be of paramount importance in doing basic research.

This was accomplished using an arrangement of electric and magnetic fields similar to that of a Penning trap, but optimized to confine single-component plasmas.

[12][13] The possibility of using thermal equilibrium statistical mechanics to describe the plasma provides a large advantage to theory.

[14] Furthermore, states near such thermal equilibria can be more easily controlled experimentally and departures from equilibrium studied with precision.

[15] Malmberg and Thomas Michael O'Neil predicted that a very cold, single-species plasma would undergo a phase transition to a body-centered cubic crystalline state.

[16] Later, John Bollinger and collaborators created such a state by laser cooling a plasma of singly ionized beryllium ions to temperatures of a few millikelvin.

[17] In other experiments, trapped pure electron plasmas are used to model the two-dimensional (2D) vortex dynamics expected for an ideal fluid.

[26] This includes ever more precise studies of antihydrogen and comparison with the properties of hydrogen[27] and formation of the di-positronium molecule (Ps

[6] In 1993, the UCSD physics department established the John Holmes Malmberg Prize in his honor.