Barbeyella minutissima is a slime mould species of the order Echinosteliales, and the only species of the genus Barbeyella. First described in 1914 from the Jura mountains, its habitat is restricted to montane spruce and spruce-fir forests of the Northern Hemisphere, where it has been recorded from Asia, Europe, and North America. It typically colonises slimy, algae-covered logs that have lost their bark and have been partially to completely covered by liverworts. The sporangia are roughly spherical, up to 0.2 mm in diameter, and supported by a thin stalk up to 0.7 mm tall. After the spores have developed, the walls of the sporangia split open into lobes. The species is one of the smallest members of the Myxogastria and is considered rare.