AbstractThe real structure of flux grown LiNbO3 crystals is investigated by etching technique, X‐ray topography, and optical polariscopic method. The main defects are microdomains, dislocations and minor impurities of V3+−ions. The crystals do not contain growth striations. The mean dislocation density is in the order of 103 cm−2. The main origin of the defects seems to be post‐growth mechanical stress. The results are discussed in comparison to the real structure typically found in the case of Czochralski crystals.