S. Andrea in Mantua is the final architectural work and the masterpiece of Leon Battista Alberti, the great 15th-century Italian humanist. As a key monument of Renaissance architecture and a seminal work for later developments including the work of Bramante and endless repetitions in Baroque Europe, the novelty of the spatial creation in S. Andrea has long been recognized. What has been obscured by the long period of construction--over 300 years--is the extent to which the existing building reflects Alberti's plan. This book, through a careful investigation of the church fabric and a sound interpretation of all relevant documents, demonstrates the fidelity of the current building to Alberti's original design. The author publishes all known documents relating to the building, including previously unpublished material, and presents new photographic documentation. The book also discusses the place of the church in Alberti's work, sources for its design in ancient, medieval and Renaissance architecture, and its role in the dynastic and civic ambitions of the ruling family of Mantua, the Gonzaga. The changes made in Alberti's plan, particularly those of the 18th century, Juvarra's dome, and Pozzo's neo-quattrocento restoration of the interior, are re-evaluated. This is the first extensive treatment of the building in English, and the first serious monograph on S. Andrea since the 19th century.