Sheep's sorrel (Rumex acetosella), also known as red sorrel, field sorrel and sour weed, is a species of plant in the buckwheat family. It is native to Eurasia and the British Isles, where it grows commonly. It is closely related to, but not the same species as common sorrel.
The leaves can be eaten raw or cooked, with the water changed to reduce its strong taste. The oxalic acid they contain lend them a somewhat sour taste. There are several uses of sheep sorrel in the preparation of food including a garnish, a tart flavoring agent, a salad green, and a curdling agent for milk in cheese-making. The leaves have a lemony, tangy or rhubarb-like tart flavor.