Oxalis dillenii, the southern wood-sorrel, slender yellow woodsorrel, or Dillen's oxalis, is a species in the woodsorrel family. Like other Oxalis species, the leaves of this plant resemble clover leaves, with three leaflets. Oxalis dillenii can be confused with other small yellow flowered species in North America, such as Oxalis stricta and Oxalis florida. The flowers have five yellow petals that are 4 to 10 mm (0.16 to 0.39 in) in length. The leaflets are 1 to 2 cm (0.39 to 0.79 in) wide with pointed hairs. The fruits are rather brown and are 1.5 to 2.5 cm (0.59 to 0.98 in). It is often considered a weed, and can be found worldwide, but likely originated in North America.