Gymnopilus bellulus is a species of mushroom in the family Hymenogastraceae. It was given its current name by American mycologist Murrill in 1917. It is odorless, bitter in taste, and regarded as inedible.
The cap is in diameter, and yellow to brown in color. The gills are yellow and turn brownish with age. The stipe is red-brown.
Gymnopilus bellulus has been found on conifer stumps and logs in the Northern United States, Tennessee, and Canada from June to January. It also occurs in Europe.