Thorium(IV) hydroxide is an inorganic compound with a chemical formula Th(OH)4.
Production Thorium(IV) hydroxide can be produced by reacting alkali metal hydroxides like sodium hydroxide and potassium hydroxide and soluble thorium salts, such as thorium nitrate.《无机化合物制备手册》.朱文祥 主编.化学工业出版社. P143. 【III-251】氢氧化钍（thorium hydroxide）Wickleder et al., pp. 70–7
Reactions New thorium(IV) hydroxide is soluble in acid but its solubility will decrease when older.
At above 470 °C, thorium(IV) hydroxide will continuously decompose and produce thorium dioxide:Wickleder et al., pp. 70–7 Th(OH)4 → ThO2 + 2 H2O
Thorium(IV) hydroxide reacts with carbon dioxide gas. Under ambient conditions this produces the hydrated oxide carbonate ThOCO3·xH2O, and under higher pressure this produces thorium carbonate hemihydrate (Th(CO3)2·½H2O).Wickleder et al., pp. 101–115
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