Liquid metal−solid semiconductor heterostructures, Hg heads combined with single-crystalline β-HgS tails, with controllable sizes and well-defined interfaces have been fabricated for the first time via one-pot synthesis. Such heterostructures can exist in water with good stability due to coordination adsorption of cysteine molecules onto the surface of both Hg and HgS through Hg−S bonds. Two-probe current−voltage curve measurements reveal that good ohmic contacts without additional resistance contacts are generated at the interfaces of Hg/β-HgS heterostructures. Only existence of ohmic contacts offers many potential applications of metal−semiconductor heterostructures in minimization of electronic devices.