Plectranthias alcocki, or Alcock's deep-reef basslet, is a species of fish in the family Serranidae occurring in the western Indian Ocean.
This species reaches a length of .
The fish is named in honor of physician-naturalist Alfred William Alcock (1859âÂÂ1933), Superintendent of the Indian Museum in West Bengal, India, in recognition of his contribution to the taxonomy of the deep-sea fauna of Indian seas.