Hexagonal boron nitride (hBN) is attracting much attention due to its tremendous applications including nanophotonic and electronic devices, substrates for two-dimensional (2D) materials, heat management materials, etc. To achieve the best device performance, large area hBN single crystals are required. Herein, large-area (>500 μm each), high-quality (defect density < 0.52/μm2) bulk hBN single crystals are grown from molten metal solutions with a temperature gradient. The narrow Raman line widths of the intralayer E2g mode peak and the interlayer shear mode, the strong and sharp phonon-assisted transition photoluminescence peaks, and the high thermal conductivity demonstrate that the hBN produced by this method has a high crystal quality with a low density of defects. Atomic force microscope images show that atomically flat layers of hBN can be produced by exfoliation. This study not only demonstrates a new strategy for growing large hBN single crystals but also provides high quality thick and thin hBN layers for nanodevice applications.