A baronet ( or ; abbreviated Bart or Bt) or the female equivalent, a baronetess (, , or ; abbreviation Btss), is the holder of a baronetcy, a hereditary title awarded by the British Crown. The title of baronet is mentioned as early as the 14th century, however, in its current usage it was created by James I of England in 1611 as a means of raising funds for the crown.

A baronetcy is the only British hereditary honour that is not a peerage, with the exception of the Anglo-Irish Black Knights, White Knights, and Green Knights (of whom only the Green Knights are extant). A baronet is addressed as "Sir" (just as is a knight) or "Dame" in the case of a baronetess, but ranks above all knighthoods and damehoods in the order of precedence, except for the Order of the Garter, the Order of the Thistle, and the dormant Order of St Patrick. Baronets are conventionally seen to belong to the lesser nobility, even though William Thoms claims that:

The precise quality of this dignity is not yet fully determined, some holding it to be the head of the nobiles minores, while others, again, rank Baronets as the lowest of the nobiles majores, because their honour, like that of the higher nobility, is both hereditary and created by patent.

Comparisons with continental titles and ranks are tenuous due to the British system of primogeniture and because claims to baronetcies must be proven; currently the Official Roll of the Baronetage is overseen by the Ministry of Justice. In practice this means that the UK Peerage and Baronetage consist of about 1,200 families (some peers are also baronets), which is roughly less than 0.01% of UK families.