Gymnopilus maritimus is a fungus species of the family Cortinariaceae first collected in northern Sardinia, Italy, in 2006. The species produces moderately sized, sturdy mushrooms of a reddish-orange colour. The cap, which can measure up to 70 millimetres (3 in) across, is covered in orange fibrils, and sometimes has small scales. The yellowish stem measures up to 110 mm (4 in) in length by 8 mm (0.3 in) in width, and sometimes shows remnants of the partial veil. The mushrooms have thick gills of a variable colour, ranging from yellow to rust but staining darker, and the yellow flesh has a mild taste. The mushrooms leave a rusty-brown spore print, while the spores themselves measure from 7.5–11.5 micrometres (0.00030–0.00045 in) in length. The species is most similar in appearance to G. ar