Pescetarianism (/ˌpɛskəˈtɛəri.ənɪzəm/ PESK-ə-TAIR-ee-ə-niz-əm; sometimes spelled pescatarianism) is a dietary practice in which seafood is the only source of meat in an otherwise vegetarian diet. The inclusion of other animal products, such as eggs and dairy, is optional. According to research conducted from 2017 to 2018, approximately 3% of adults worldwide are pescetarian.
Seafood is any form of sea life regarded as food by humans, prominently including fish and shellfish. Shellfish include various species of molluscs (e.g., bivalve molluscs such as clams, oysters, and mussels, and cephalopods such as octopus and squid), crustaceans (e.g. shrimp, crabs, and lobster), and echinoderms (e.g. sea cucumbers and sea urchins). Historically, marine mammals such as cetaceans (whales and dolphins) as well as seals have been eaten as food, though that happens to a lesser extent in modern times. Edible sea plants such as some seaweeds and microalgae are widely eaten as sea vegetables around the world, especially in Asia.
Seafood is an important source of (animal) protein in many diets around the world, especially in coastal areas. Semi-vegetarians who consume seafood as the only source of meat are said to adhere to pescetarianism.