An acidic (acid-forming) oxide is a non-metal oxide that forms an oxoacid when it reacts with water, or that is neutralised by bases. Such oxides behave as acids and are typical of non-metals on the right of the periodic table. Carbon dioxide is an acidic oxide, forming carbonic acid with water; it contrasts with a basic oxide, which is formed by a metal.

酸性氧化物是与水反应生成含氧酸、或能被碱中和的非金属氧化物。这类氧化物表现为酸,是周期表右侧非金属的典型氧化物。二氧化碳是酸性氧化物,与水生成碳酸;它与由金属形成的碱性氧化物相对。