This introductory chapter sets the stage for analysing the economic history of Italian pilgrimages in the nineteenth and twentieth centuries, highlighting religious tourism as a precursor to mass tourism in Italy. Even though the latter blossomed during the economic boom years of the 1950s and 1960s, this volume argues that much of the groundwork for its development was laid by organized Catholic pilgrimages between Italian Unification and World War II. The chapter discusses the evolving definitions of pilgrimage and religious tourism, emphasizing their intersections and historiographical challenges. It presents the great wealth of published and unpublished sources on which the historical reconstruction is based and introduces the three key case studies addressed in the volume—Rome, Lourdes, and the Holy Land—to illustrate how religious travel transformed through improved transportation, economic developments, and changing social contexts. It argues that pilgrimage increasingly became a collective and structured experience drawing on factors relating to mobility, consumption, and identity-building. In conclusion, the chapter advocates for a broad and inclusive definition of religious tourism that reflects the diversity of practices and motivations observed in the field.