Lopha cristagalli, the cockscomb oyster, is a species of marine bivalve molluscs in the family Ostreidae.

It has a variable coloration, dark to light purple, and it is a thick, strongly ribbed, and slightly inequivalve shell.

These molluscs are stationary epifaunal suspension feeders, as they feed filtering sea water to extract the nutrients.

This species is widespread in the Indo-West Pacific, from East Africa, including Madagascar, Mauritius, the Red Sea, Seychelles, and the Persian Gulf, to Micronesia; north to Japan and south to Papua New Guinea and Indonesia.

It lives on coral reefs in shallow subtidal waters at depths of 5 to 30 m.