The little bittern has a length of 33–38 centimetres (13–15 in) and a wing span of 52–58 centimetres (20–23 in).
It is the smallest of the breeding herons of Europe and is characterised by its tiny size, long and sharp bull and thick neck.
The male's are distinctively patterned and both sexes show pale forewing panels.
The males have black with a faint green sheen on the crown, nape, back, tail and scapulars.
The underparts are pale buff and the wing has a pinkish buff oval shaped panel which contrasts with the otherwise black wings and is formed by the inner wing coverts.
The underwing is completely whiteish in colour.
The female is duller than the male and has brownish black upperparts with paler feather margins visible at close range.
The underparts of the female are not as clean as those of the male and are streaked with dark buff and brown.
The female's wing panel is less obvious than the male's.
The juveniles are duller and more rufous than the females and are more heavily streaked on both their upperparts and underparts, including their wing coverts.
The little bittern has a length of 33–38 centimetres (13–15 in) and a wing span of 52–58 centimetres (20–23 in). It is the smallest of the breeding herons of Europe and is characterised by its tiny size, long and sharp bull and thick neck. The male's are distinctively patterned and both sexes show pale forewing panels. The males have black with a faint green sheen on the crown, nape, back, tail and scapulars. The underparts are pale buff and the wing has a pinkish buff oval shaped panel which contrasts with the otherwise black wings and is formed by the inner wing coverts. The underwing is completely whiteish in colour. The female is duller than the male and has brownish black upperparts with paler feather margins visible at close range. The underparts of the female are not as clean as those of the male and are streaked with dark buff and brown. The female's wing panel is less obvious than the male's. The juveniles are duller and more rufous than the females and are more heavily streaked on both their upperparts and underparts, including their wing coverts.
Little bittern