Stud Pin, and Pneumatic Tire

A stud pin includes a tip including a tip end surface configured to come into contact with a road surface and a trunk portion that supports the tip and extends in one direction. The trunk portion includes an upper flange disposed at a first end of the trunk portion, the tip being fixed to the upper flange, and a lower flange disposed at a position to a side opposite the upper flange of the trunk portion. An upper end surface of the upper flange from which the tip protrudes includes a recessed surface, the recessed surface including a smooth inclined surface recessing in a curved manner or a linear manner toward the lower flange with advancement toward a protruding base portion of the tip.