Dianthus barbatus, the sweet William,[2] is a species of flowering plant in the family Caryophyllaceae, native to southern Europe and parts of Asia.

It is a herbaceous biennial or short-lived perennial plant growing to 13–92 cm tall, with flowers in a dense cluster of up to 30 at the top of the stems.

The exact origin of its English common name is unknown but first appears in 1596 in botanist John Gerard's garden catalogue.

Sweet William grows in the mountains of southern Europe from the Pyrenees east to the Carpathians and the Balkans, with a variety disjunct in northeastern China, Korea, and southeasternmost Russia.

[5][7][8] There are two varieties:[5] Many legends purport to explain how sweet William acquired its English common name, but none is verified.

As a result of the Duke's victory at the Battle of Culloden and his generally brutal treatment of the king's enemies, it is also claimed that the Scots sometimes call the flower "stinking Billy".

Sweet William is a popular ornamental plant in gardens, with numerous cultivars and hybrids selected for differing flower colour, ranging from white, pink, red, and purple to variegated patterns.

Sweet William is a good candidate for a naturalistic garden because its nectar attracts birds, bees, and butterflies.