Compared to Pb(Zr1−xTix)O3 (PZT) polycrystalline ceramics, relaxor-PT single crystals offer significantly improved performance with extremely high electromechanical coupling and piezoelectric coefficients, making them promising materials for piezoelectric transducers, sensors and actuators. The recent advances in crystal growth and characterization of relaxor-PT-based ferroelectric single crystals are reviewed in this paper with emphases on the following topics: (1) the large crystal growth of binary and ternary relaxor-PT-based ferroelectric crystals for commercialization; (2) the composition segregation in the crystals grown from such a solid-solution system and possible solutions to reduce it; (3) the crystal growth from new binary and ternary compositions to expand the operating temperature and electric field; (4) the crystallographic orientation dependence and anisotropic behaviors of relaxor-PT-based ferroelectriccrystals; and (5) the characterization of the dielectric, elastic and piezoelectric properties of the relaxor-PT-based ferroelectriccrystals under small and large electric fields.