Onion-stalk Parasol 
Onnia subtriquetra 
Orange Birch Bolete 
Orange bonnet 
Orange Coral 
Orange Gilled Waxcap 
Orange Jelly Spot 
Orange milkcap 
Orange Moss Agaric 
Orange mycena 
Orange Oak Bolete 
Orange oyster 
Orange Pinwheel 
Orange Polypore 
Orange pore fungus 
Orange pore fungus 
Orange Waxcap 
Orange webcap 
Orange-latex Milky 
Ornate-stalked bolete 
Osmoporus odoratus 
oudemansiella canari 
Oudemansiella gigaspora 
Overflowing Slimy Stem