Marpissa muscosa is a species of jumping spider.

On average, females have body length ranging from 7.5–14mm, whereas males have a body length ranging from 6–8.1mm. Both sexes are coloured grey to brown. The whole spider has a furry appearance and is flattened in shape.

The species builds a kind of nest under the bark of dead trees. Up to 100 of these nests can occur side by side. Like other species of Marpissa spiders, it demonstrates a social hierarchy: weaker animals will acknowledge their inferiority by strutting their front legs and slowly retreating from the scene. Early environmental conditions shape personality types in the developing spiders.

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