To provide a potassium lithium niobate piezoelectric single crystal which has a large electromechanical coupling factor and a low acoustic velocity.

In the potassium lithium niobate piezoelectric single crystal having a composition of main components, comprising, by mol, 26-34% potassium oxide, 19-27% lithium oxide, and 45-53% niobium oxide, an amount of ≤5%(0 is not included) of the content of the niobium oxide is substituted for molybdenum oxide. Further, when the single crystal is grown, a pulling-up or pulling-down method from a melt is utilized.