Katamari Damacy (塊魂 Katamari Damashii, which roughly translates to clump soul) is a third-person puzzle-action video game that is developed and published by Namco for the PlayStation 2 video game console. It was first released in Japan, and then later in South Korea and North America. The game resulted from a school project from the Namco Digital Hollywood Game Laboratory, and was developed for less than $1 million. In designing Katamari Damacy, the development team aimed to maintain four key points: novelty, ease of understanding, enjoyment, and humor.

The player controls the Prince as he rolls the katamari around houses, gardens, and towns in order to meet certain parameters set by the King of All Cosmos. The player uses the two analog sticks on the DualShock controller in a manner similar to the classic arcade game Battlezone to control the direction the katamari rolls. Other controls can be triggered by the player to gain a quick burst of speed, flip the Prince to the other side of the katamari, and more.[3]

Objects that are smaller than the katamari will stick to it when the player comes into contact with them, while greater objects can be hurdles; colliding at high speed with any may cause objects to fall off the katamari, slowing the player's progress. The game uses size, weight, and surface area to determine if an object will stick to the katamari. This allows slender objects, such as pencils, that are wider than the katamari, to be picked up, and these will alter how the katamari rolls until more objects are picked up.[3] Animals such as cats will chase the katamari, knocking things from it, but once the katamari is great enough, it will scare the animals away, and they can be rolled up once they are chased down. As objects stick to the katamari, the katamari will grow, eventually allowing objects that were once hurdles to be picked up, and creating access to areas that were formerly blocked. In this manner, the player might start the game by picking up thumbtacks and ants, and slowly work up to the point where the katamari is picking up buildings, mountains, and clouds.[3]