A pneumatic tire has a main groove (3) provided to a tread part (2). A groove bottom (12) includes a protrusion portion (13) that is convex outward in a tire radial direction. The protrusion portion (13) continues along the main groove (3). The width (W3) of the protrusion portion (13) in a direction perpendicular to a groove center line (G1) of the main groove (3) is 50% to 100% of the groove width (W1) of the main groove (3). The protrusion portion (13) juts outward in the tire radial direction from an imaginary groove bottom (12A) that connects an inner end (10i) of a first groove wall (10) and an inner end (11i) of a second groove wall (11) in a straight line, and the cross-sectional area of the protrusion portion (13) is 3% to 15% of the transverse cross-sectional area of the main groove (3).