Single crystals of lanthanide iodates have been quickly grown by decomposition of the corresponding periodates under hydrothermal conditions. Single crystal X-ray diffraction showed that two structure types form with the elements from Pr-Yb, an anhydrous form for Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er and a dihydrate for Eu, Gd, Dy, Er, Tm, Yb. A detailed structure study is presented for one representative of each of these types, along with structure type and lattice parameters for the other materials. Tb(IO3)(3): Space group P2(1)/c, Z = 4, lattice dimensions at 120 K: a = 7.102(1), b = 8.468(1), c = 13.355(2) Angstrom, beta = 99.67(1)degrees; R1 = 0.034. Yb(IO3)(3) . 2H(2)O: Space group P (1) over bar, Z = 2, lattice dimensions at 120 K: a = 7.013(1), b = 7.370(1), c = 10.458(2) Angstrom, alpha = 95.250(5), beta = 105.096(5), gamma = 109.910(10)degrees; R1 = 0.024.