The chapter addresses the role and content of Spanish constitutional identity. It first considers the stance of the Spanish Constitutional Court. In this regard, Spain joins the list of EU Member States whose constitutional courts do not accept the principle of primacy’s effectiveness in EU law vis-à-vis the Constitution. In order to contain the unlimited scope of that principle, the Constitutional Court has come up with an original and controversial distinction between the primacy of EU law and the supremacy of the Constitution. It also acknowledges that there is a core of the Constitution – its constitutional identity – that falls outside the scope of primacy. Its content lies in the respect for state sovereignty, for basic constitutional structures, and for the system of core values and principles in the Constitution, where fundamental rights acquire their own substantive nature. The chapter also examines the role of constitutional identity in the context of the Catalan secessionist movement. It considers that ensuring the state’s territorial integrity is an indispensable part of constitutional identity, whilst providing an obligation incumbent on the EU under Art. 4(2) TEU.