Santiago Calatrava Valls, born 28 July 1951, is a Spanish architect, sculptor and structural engineer whose principal office is in Zürich, Switzerland. Classed now among the elite designers of the world, he has offices in Zürich, Paris, Valencia, and New York City.

Calatrava was born in Benimàmet, an old municipality now integrated as an urban part of Valencia, Spain, where he pursued his undergraduate architecture degree at the Polytechnic University of Valencia along with a post-graduate course in urbanism. Calatrava's early career was dedicated largely to bridges and train stations, whose designs elevated the status of civil engineering projects to new heights. 

His Montjuic Communications Tower in Barcelona, Spain (1991) in the heart of the 1992 Olympic site, as well as the Allen Lambert Galleria in Toronto, Canada (1992), were important works and turning points in his career, leading to a wide range of commissions. The Quadracci Pavilion (2001) of the Milwaukee Art Museum was his first building in the US. Calatrava's entry into high-rise design began with an innovative 54-story-high twisting tower called Turning Torso (2005), located in Malmö, Sweden.

Calatrava is currently designing the future train station – World Trade Center Transportation Hub – at the rebuilt World Trade Center in New York City.

Calatrava's style has been heralded as bridging the division between structural engineering and architecture. In the projects, he continues a tradition of Spanish modernist engineering that includes Félix Candela and Antonio Gaudí. Nonetheless, his style is also very personal and derives from numerous studies of the human body and the natural world.