Marconi's early claims of transatlantic wireless communication were initially met with skepticism from some scientists and engineers. Some doubted the feasibility of such long-distance transmission, while others questioned the reliability of his equipment.

Marconi faced numerous patent disputes and legal challenges from other inventors who claimed to have made similar discoveries. He vigorously defended his patents and intellectual property rights.

Marconi's association with the Italian Fascist regime generated controversy, particularly after World War II. His support for Mussolini's policies has been criticized by some historians and biographers, who argue that it tarnished his legacy.

Despite the controversies, Marconi's legacy as a pioneer of wireless communication remains strong. He is widely recognized as one of the most important figures in the history of telecommunications, and his inventions have had a profound impact on modern society.