The dunnock (Prunella modularis) is a small passerine, or perching bird, found throughout temperate Europe and into Asian Russia. Dunnocks have also been successfully introduced into New Zealand. It is the most widespread member of the accentor family; most other accentors are limited to mountain habitats. Other, largely archaic, English names for the dunnock include hedge accentor, hedge sparrow, hedge warbler, and titling.

The dunnock was described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae. He coined the binomial name of Motacilla modularis. The specific epithet is from the Latin modularis "modulating" or "singing". This species is now placed in the genus Prunella that was introduced by the French ornithologist Louis Pierre Vieillot in 1816.

The name "dunnock" comes from the English dun (dingy brown, dark-coloured) and the diminutive ock (thus, the original "little brown bird"), while "accentor" is from post-classical Latin and means a person who sings with another. The genus name Prunella is from the German Braunelle, "dunnock", a diminutive of braun, "brown".

Seven subspecies are accepted by the IOC list:

Acceptance of these seven subspecies has not been universal; Shirihai & Svensson (2018) accept only three subspecies, P. m. occidentalis (including P. m. hebridium), P. m. modularis (including P. m. euxina, P. m. mabbotti), and P. m. obscura (including P. m. fuscata). Another study however recently suggested that dunnock might be better treated as three species, with P. m. mabbotti and P. m. obscura being elevated from subspecies status to separate species.

A robin-sized bird, the dunnock typically measures 13–14.5 cm (5.1–5.7 in) in length. It has a brown back streaked blackish, somewhat resembling a small house sparrow. Like that species, the dunnock has a drab appearance which may have evolved as camouflage to avoid predation. It is brownish underneath, and has a fine pointed bill. Adults have a dull grey head, and both sexes are similarly coloured; juveniles are browner on the head, looser, 'fluffy' feathering, and more obviously streaked overall. Unlike any similar sized small brown bird in Europe, dunnocks exhibit frequent wing flicking, especially when engaged in territorial disputes or when competing for mating rights. This gave rise to the old nickname of "shufflewing".

The main call of the dunnock is a shrill, persistent tseep along with a short, weak trilling note, which betrays the bird's otherwise inconspicuous presence. The song is rapid, thin and tinkling, a sweet warble.

Dunnocks are native to large areas of Eurasia, inhabiting much of Europe and southwest Asia including Lebanon, northern Iran, and the Caucasus. It is the only accentor commonly found in temperate lowland areas; the others all inhabit upland areas, or (Siberian accentor) subarctic lowlands. Favoured habitats include woodlands, shrubs, gardens, and hedgerows where they typically feed on the ground, often seeking out detritivores as food.