While many ancient Greek philosophers suspected the Earth revolved around the Sun, the first person to publicly propose and defend a heliocentric model of the solar system was Nicolaus Copernicus.

He published his groundbreaking work, *De Revolutionibus Orbium Coelestium* (On the Revolutions of the Heavenly Spheres), in 1543, shortly before his death.

It's important to note that Copernicus wasn't the first to suggest this idea. Aristarchus of Samos had proposed a heliocentric model over 1700 years earlier, but his work was largely ignored. Copernicus built upon the ideas of previous thinkers and presented a more comprehensive and mathematically sound argument for a Sun-centered universe.