A heavy duty tire includes a tread portion provided with a pair of circumferential main grooves including at least one zigzag groove, lateral grooves extending between the main grooves to form center blocks therebetween, and lug grooves. Each lug groove includes an axially inner portion connecting to the zigzag groove while curving toward a first circumferential direction of the tire. The lug groove has a first groove edge disposed on a side of the first circumferential direction and a second groove edge facing against the first groove edge. The first groove edge is connected to an axially outer groove edge of the zigzag groove. The second groove edge is connected to an axially inner groove edge of the zigzag groove. The lug groove includes a constant groove width, and a groove-bottom width smoothly decreasing axially inward from the tread edge.