Tricholoma sulphureum, also known as the stinker,[1] sulphur knight or gas agaric, is an inedible or mildly poisonous mushroom found in woodlands in Europe.

It has a distinctive bright yellow colour and an unusual smell likened to coal gas.

John Ramsbottom reports that it has a complex smell that has been likened variously to Jasmine, Narcissus, Hyacinth, Hemerocallis flava, Lilac, Tagetes, decayed hemp or coal gas, as well as described as nauseating or foetid.

It could be confused with the darker T. equestre, though the latter has a sticky cap, white flesh, thin crowded gills, and a mealy smell.

Tricholoma sulphureum is found in deciduous woods, particularly beech, and can occur anytime from spring until autumn.