The diademed sandpiper-plover or diademed plover (Phegornis mitchellii ) is a species of bird in the plover family Charadriidae. It is monotypic within the genus Phegornis. The relationship of this species to other plovers is uncertain, a 2010 study suggested it may be related to the Australian dotterels.

The species is found in the Puna grassland ecoregions of the Andes Mountains from Argentina and Chile, through Bolivia to Peru. In this habitat it prefers mossy tundra, high-altitude grassland, bogs and swamps. It is an altitudinal migrant, breeding between 3,500–5,000 m (11,500–16,400 ft) above sea-level, but wintering at 2,000 m (6,600 ft).

The diademed sand-piper-plover is a small compact plover, 16.5–19 cm (6.5–7.5 in) in length and weighing 28–46 g (0.99–1.62 oz). It has a black head with a white stripe above the eye meeting at the crown, a chestnut neck, a white throat and chest barred in black, and grey upperparts. The wings are short and the flight undulating. The sexes are alike and the juvenile has a grey head, less distinct barring on the front and brown upperparts.

They breed in the summer months, laying two eggs, olive-grey with black spots, in a circular nest of grasses. The downy chicks are dark brown, marbled with black above and lighter below.

The species is poorly known and uncommon, and rarely recorded. While its habitat is thought to be secure, it is possible that overgrazing is a threat.