Translation and interpreting are deeply interconnected with bilingualism. Without high degrees of bilingualism, neither translation nor interpreting is feasible. This does not mean, however, that either translation or interpreting is a by-product of bilingualism. Rather it means that high attainment in bilingualism is a precondition for highly proficient translation/interpreting. The relationship between language ability, types of bilingualism, and translation/interpreting performance has not been sufficiently researched. This entry consists of different parts, each dealing with another aspect: (i) types of bilinguals; (ii) bilingual typologies and translation/interpreting professionals; (iii) bilingual typologies and translation/interpreting classrooms; (iv) challenges in research; and (v) research in bilingual youngsters, translation, and interpreting.