The present invention is directed to lanthanide vanadate crystals having the formula LnVO.sub.4, wherein Ln is selected from La, Nd, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and combinations of at least two thereof, made by a hydrothermal method for a wide variety of end-use applications. The present method requires reacting a source of Ln.sup.3+ ions and a source of VO.sub.4.sup.3+ ions, wherein Ln is selected from the group consisting of La, Nd, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and combinations of at least two thereof, in an aqueous solution at a temperature of from about 350.degree. C. to about 600.degree. C. and at a pressure of from about 8 kpsi to about 40 kpsi, the aqueous solution comprising hydroxide ions at a concentration of from about 0.01 to about 5 molarity. Specifically, when made by the present hydrothermal method, single crystals of sufficient size for use in a variety of optical applications are readily formed.