Beryllium sulfate tetrahydrate (BeSO4⋅4H2O) has been found to be phase matchable for frquency doubling of 5321‐A˚ radiation. The water white crystal is highly transparent from 1900 to 13 700 A˚. The nonlinear optical constant was measured to bed36(BeSO4⋅4H2O) = (0.62±0.06)xd36(KD*P).