In this entry, we explore different conceptions of identity under a public law perspective. We identify overlapping, but inescapably linked, concepts of identity, originating from different angles of exploration: constitutional identity as the constitutional core safeguarded by unamendable provision; constitutional identity as emerging from the legal shaping of citizenship law; constitutional identity as an evolving legal concept. Moreover, we explore constitutional identity as a global context with specific regional declinations and devote specific attention to the forefront of the legal debate around constitutional identity, ie the European Union.