Oxalis ( (British English) or (American English)) is a large genus of flowering plants in the wood-sorrel family, Oxalidaceae, comprising over 550 species. The genus occurs throughout most of the world, except for the polar areas; species diversity is particularly rich in tropical Brazil, Mexico, and South Africa.

Many of the species are known as wood-sorrels (also as wood sorrels or woodsorrels) as they have an acidic taste reminiscent of the sorrel proper (Rumex acetosa), which is not closely related. Some species are called yellow sorrels or pink sorrels after the colour of their flowers instead. Other species are colloquially known as false shamrocks, and some called sourgrasses. For the genus as a whole, the term oxalises is also used.

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