This article analyses the role played by the Monarchy in the Spanish transition to democracy. The Crown is looked on as both an Institution and a person embodying it. The Introduction considers the authoritarian character of Franco's regime; sections 1 and 2 focus on the Spanish constitutional and historical context of the 1960s and 1970s. The instruments and consequences of the Crown's intervention in the transition (Nov. 1975 - Dec. 1976) are looked at in sections 3 and 4. Although the "M(onarchy) factor" cannot by itself provide a comprehensive explanation of the transition, the article contends that it is essential for a proper understanding of the political change, and that the reform-oriented policy of the King affected both the form (pacific) and the content (democratic) of the transition to democracy.