We present the results of an all-sky volume-limited survey of 1121 M dwarfs, known via trigonometric parallaxes to lie within 25 pc of the Sun, for stellar companions at separations 2" to 600". In addition to a literature search for known companions, I-band images, primarily from the CTIO/SMARTS 0.9m and the Lowell 42in telescopes, were obtained in order to search these systems for companions at separations of 2" to 180". A complementary reconnaissance of wider companions to 600" was also done via the blinking of SuperCOSMOS BRI images.

We find a stellar multiplicity fraction of 27.4 (1.3)% for M dwarfs, with the majority of systems having companions at angular separations less than 2". We find a peak in the log-projected separation distribution of the companions at 26 AU, i.e., distances on the scale of our Solar System, with a weak trend of smaller projected separations for lower mass primaries. A hint that M dwarf multiplicity may be a function of age/composition was revealed, with faster moving

(and generally older) systems being multiple slightly less often. We calculate that at least 16% of M dwarf mass is made up of the stellar companions in these multiple systems. Finally, we show that the normal mass function for M dwarfs increases to the end of the main sequence.