The famous architect behind the design of St. Peter's Basilica in Rome was Michelangelo Buonarroti. Although the basilica's construction began before he joined the project, Michelangelo’s vision was pivotal in its design. He served as the chief architect from 1546 until his death in 1564, implementing significant structural changes, including the grand dome that has become a defining feature of the basilica. His artistic mastery and understanding of space allowed for a harmonious blend of architecture and sculpture, making St. Peter's Basilica a quintessential masterpiece of Renaissance art and a major pilgrimage site for Catholics.