Gigantism, also known as giantism (from Greek Greek language,Greek ,
 gigas, gigantas "giant"), is a condition characterized by excessive growth and height significantly above average. This condition is caused by an over production of human growth hormone.
The term is typically applied to those whose height is not just in the upper 1% of the population.

 
Many of those who have been identified with gigantism have suffered from multiple health problems involving their circulatory or skeletal system.

The term is seldom applied to those who are simply "tall" or "above average" whose heights appear to be the healthy result of normal genetics and nutrition. It is usually caused by a tumor on the pituitary gland on the brain. It causes growth of the hands, face, and feet.

In the past, while many of them were social outcasts because of their height, some found employment in Friedrich Wilhelm I's famous Potsdam Giants regiment.