碱式碳酸铋（化学式：Bi₂O₂(CO₃)），别名次碳酸铋；碳酸氧铋。

白色或微黄色无臭无味粉末，见光逐渐变为褐色。难溶于水、乙醇及其它有机溶剂，易溶于盐酸、硝酸和浓乙酸中。溶于氯化铵溶液，微溶于碱金属碳酸盐溶液。加热灼烧时分解为氧化铋和二氧化碳。

在自然界中以泡铋矿的形式出现。其晶体结构中含有 Bi-O 层和 CO₃ 层。

Bismuth subcarbonate (BiO)₂CO₃, sometimes written Bi₂O₂(CO₃) is a chemical compound of bismuth containing both oxide and carbonate anions. Bismuth is in the +3 oxidation state. Bismuth subcarbonate occurs naturally as the mineral bismutite. Its structure consists of Bi-O layers and CO₃ layers and is related to kettnerite, CaBi(CO₃)OF. It is light sensitive.