What explains the treatment of ethnic minorities in Southeast Asia? This Element conceptually disaggregates ethnicity into multiple constituent markers - specifically language, religion, and phenotype. By focusing on the interaction between these three ethnic markers, Liu and Ricks explore how overlap between these markers can affect whether a minority integrates within a broader ethnic identity; successfully extracts accommodation as unique group; or engages in a contentious and potentially violent relationship with the hegemon. The argument is tested through six case studies: (1) ethnic Lao in Thailand: integration; (2) ethnic Chinese in Thailand: integration; (3) ethnic Chinese in Malaysia: accommodation; (4) ethnic Malays in Singapore: accommodation; (5) ethnic Malays in Thailand: contention; and (6) ethnic Chinese in Indonesia: contention.