Constitutional identity is the buzz word of the day in constitutional theory and European politics. Member States invoke it to question the primacy of EU law and sometimes even to justify illiberal constitutional politics. Nevertheless, its meaning remains vague. This paper will shed light on constitutional identity by contrasting it with important conceptions of collective identity, such as Montesquieu’s esprit général, Kymlicka’s societal culture and Rosenfeld’s identity of the constitutional subject. It compares the theoretical approaches along several dimensions: (1) The origins of identity; (2) its subject; (3) its content; (4) the empirical sources expressing identity; (5) its changeability; and (6) its value. The aim is a sharper conceptualization of the constitutional conception of collective identity that can contribute to the academic debate about collective identities and offer a new perspective on this notion with the potential to shape Europe’s future.