Memory psychophysics treats the functional relations between physical stimuli and their remembered mental representations. The name indicates the coalescence of the parent disciplines of memory and psychophysics into a new discipline explicating the correspondence between objective and mental depictions of the referent stimulus. This article documents the young history of research, but long past of ideas, of memory psychophysics. It then summarizes the results obtained and the models suggested within unidimensional mnemophysics concerned with deriving remembered magnitude as a function of stimulus intensity. An exposition of multidimensional mnemophysics follows, treating principles of stimulus integration and organization in perception and memory. The article concludes with a brief review of the research on stimulus comparison and other, process-based, studies of memory psychophysics.