Iccus of Tarentum was a Greek athlete and philosopher from the 5th century BCE. A native of the southern Italian city of Tarentum, he was an Olympic victor in the pentathlon. He is primarily remembered not just for his athletic success, but for his legendary self-discipline. Ancient sources report that he practiced extreme asceticism during training, abstaining from sex and following a strict diet to conserve his strength. This lifestyle of temperance led later writers to associate him with Pythagorean philosophy, which emphasized bodily and ethical discipline. The philosopher Plato mentions Iccus as a model of self-control.

No writings by Iccus survive today. According to a later Byzantine source, he wrote a work on athletic training, but it is lost. He is known only through references by other authors.

Iccus is a significant figure for understanding the connection between Greek athletics and philosophy. He represents the ideal of the "athlete-philosopher" who applied intellectual principles to physical training. His reputation made him a lasting symbol of moderation and self-mastery. Later medical writers also cited him as an early example of using diet and a disciplined regimen to optimize athletic performance.