An acoustic wave resonator includes a support substrate, a piezoelectric layer that is disposed on the support substrate and is a rotated Y-cut X-propagation lithium tantalate of which a cut angle is within a range of greater than 50° and less than 150°, and a pair of comb-shaped electrodes disposed on the piezoelectric layer, each of the comb-shaped electrodes including a plurality of electrode fingers, an average pitch of the electrode fingers of one of the comb-shaped electrodes being equal to or greater than ½ of a thickness of the piezoelectric layer.