Heliocentrism is the astronomical model in which the Sun is at or near the center of the Solar System, with Earth and other planets orbiting around it. It stands in contrast to Geocentrism, which places Earth at the center. The heliocentric model is the foundation of modern astronomy and planetary science.

In the heliocentric model, Earth and the other planets travel in elliptical orbits around the Sun, a relationship governed by Newtonian gravity and later refined by Einstein's general relativity. The Sun contains over 99.8% of the Solar System's total mass, making it the dominant gravitational body. Earth completes one orbit approximately every 365.25 days, and rotates on its own axis once every 24 hours — accounting for the apparent daily movement of the Sun across the sky. The model explains a wide range of observable phenomena: the phases of Venus, the apparent retrograde motion of outer planets, stellar parallax, and the predictable positions of planets across centuries. These predictions have been verified repeatedly through direct observation, spacecraft navigation, and satellite positioning systems that depend on heliocentric calculations for their accuracy.

Ancient Greek astronomers, including Aristarchus of Samos (~310–230 BC), proposed heliocentric ideas, but the geocentric model of Ptolemy dominated Western and Islamic astronomy for over a millennium. Nicolaus Copernicus formally revived heliocentrism in his 1543 work De revolutionibus orbium coelestium. Tycho Brahe, Johannes Kepler, and Galileo Galilei advanced and defended the model through the 16th and 17th centuries, with Kepler's laws of planetary motion providing the mathematical framework that Newton later explained through universal gravitation. For more detail, see Heliocentrism - History.

Heliocentrism, in its modern form, is among the most thoroughly confirmed models in all of science. It is not merely a useful approximation — spacecraft trajectories, GPS satellite timing corrections, and astronomical predictions all depend on and confirm heliocentric mechanics to extraordinary precision. Within the broader context of general relativity, the Solar System has no absolute center, but the Sun serves as the practical gravitational center for all Solar System dynamics.

• The conflict between Galileo and the Catholic Church over heliocentrism is discussed at Galileo and Heliocentrism.
• The historical Catholic Church position on heliocentrism, including its theological basis and evolution, is covered at Heliocentrism - Historical Catholic Viewpoint.
• The nature and limits of scientific consensus as applied to heliocentrism, including fringe dissent, is examined at Heliocentrism - Scientific Consensus.