Caloboletus rubripes, commonly known as the red-stipe bolete or the red-stemmed bitter bolete, is a mushroom in the family Boletaceae. It was known as Boletus rubripes until 2014. Fruit bodies (mushrooms) are robust, with caps up to 18 cm (7.1 in) in diameter, atop thick stipes 5–12 cm (2.0–4.7 in) long. Mushrooms are non-toxic, but is so bitter as to be inedible. The mushroom flesh has a very strong bluing reaction when cut or damaged. and forms mycorrhizal relationships, primarily with conifers. It can be differentiated from similar boletes by its cap color and non-reticulate stipe.