碳酸氢钠（化学式：NaHCO₃），俗称小苏打、苏打粉、重曹、焙用碱等，白色细小晶体，在水中的溶解度小于苏打，呈弱碱性。

50℃以上开始逐渐分解生成碳酸钠、二氧化碳和水，270℃时完全分解。碳酸氢钠是强碱与弱酸经中和作用后生成的酸式盐，溶于水时呈现弱碱性。

常利用此特性作为食品制作过程中的膨松剂。

碳酸氢钠，是易溶于水的白色碱性粉末，在与水结合后开始起作用释出二氧化碳CO₂，在酸性液体（如果汁、可乐）中反应更快，而随着环境温度升高，释出气体的作用愈快。碳酸氢钠水溶液呈弱碱性，俗称小苏打及焙用碱。

Sodium bicarbonate (IUPAC name: sodium hydrogen carbonate) is a chemical compound with the formula NaHCO₃. It is a salt composed of sodium ions and bicarbonate ions. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite. It is a component of the mineral natron and is found dissolved in many mineral springs. It is among the food additives encoded by European Union, identified as E 500. Since it has long been known and is widely used, the salt has many related names such as baking soda, bread soda, cooking soda, and bicarbonate of soda. In colloquial usage, the names sodium bicarbonate and bicarbonate of soda are often truncated. Forms such as sodium bicarb, bicarb soda, bicarbonate, bicarb, or even bica are common. The word saleratus, from Latin sal æratus meaning "aerated salt", was widely used in the 19th century for both sodium bicarbonate and potassium bicarbonate.