Thallium(I) carbonate is the inorganic compound with the formula Tl<sub>2</sub>CO<sub>3</sub>. It is a white, water-soluble salt. It has no or very few commercial applications. It is produced by treatment of thallous hydroxide with CO<sub>2</sub>.
Like other thallium compounds, it is extremely toxic, with an oral median lethal dose of 21 mg/kg in mice. Due to its toxicity, it is listed in the United States List of Extremely Hazardous Substances as of 2007.