We report that pyramidal inversion of trivalent phosphines may be catalyzed by single electron, oxidation. Specifically, a series of P-stereogenic (aryl)-methylphenyl phosphines are shown to undergo rapid racemization at ambient temperature when exposed to catalytic quantities of a single electron oxidant in solution. Under these conditions, transient phosphoniumyl radical cations (R3P center dot+) are formed, and computational models indicate that the pyramidal inversion barriers for these open-shell intermediates are on the order of similar to 5 kcal/mol. The observed 10(20)-fold rate enhancement over uncatalyzed pyramidal inversion opens new opportunities for the dynamic stereochemistry of phosphines and may hold additional implications for the configurational stability of P-stereogenic phosphine ligands on high-valent oxidizing transition metals.