Thallium(I) chloride, also known as thallous chloride, is a chemical compound with the formula TlCl. This colourless solid is an intermediate in the isolation of thallium from its ores. Typically, an acidic solution of thallium(I) sulfate is treated with hydrochloric acid to precipitate insoluble thallium(I) chloride. This solid crystallizes in the caesium chloride motif.