OCG stands for Official Card Game, which is the version of the Yu-Gi-Oh! trading card game played in East and Southeast Asia, including Japan, China, and Korea. The cards in OCG are printed in Japanese, Korean, and Chinese, and on rare occasions, English. On the other hand, TCG stands for Trading Card Game, which is the version of the game played in the Americas, Europe, the Middle East, Africa, and Oceania. The cards in TCG are printed in English, Portuguese, Spanish, French, German, and Italian. Each version has its own banlists and unique products.

It is important to note that OCG can also stand for Organized Crime Group, which refers to a group of individuals who act together to further the carrying on of criminal activities. In this context, participating in an OCG can lead to prosecution for a number of different offenses, including conspiracy offenses and substantive offenses.

Other meanings of OCG include Operating Capital Generation, Operational Coordination Group, Offline Content Generator, and Oral Cholecystography.