Koopas (once "the Koopa") are a category of turtle-like creatures, most of which form the Turtle Tribe or Koopa clan. There are many different types of Koopas, the most common being Koopa_Troopas. Most Koopas operate in a hierarchy-based grouping system. Bowser is the leader of the Koopa Troop, which has invaded Mushroom Kingdom many times and has control over most of the Koopas in the Mario franchise [ Mario_(series) ], beginning in Super_Mario_Bros._1. where, according to an interpretation of the story of the Japanese game's manual during the English localization that saw Koopa (クッパ) as the name of the group of turtles instead of the name of Bowser, they were known for their "black magic." Said interpretation has since been rectified, with Koopa being acknowledged to be the Japanese name of Bowser, but the concept of Koopas as a group of turtles in the West remains, while Nintendo in Japan consistently refers to Koopa as the name of Bowser and to the Turtle Tribe (カメ族) as the group to which the various turtles belong. Many of these same Koopas are members of the Koopa Troop and have different tasks in the organization based on the abilities of their particular class. For example, Koopa_Troopas tend to be assigned as basic foot soldiers alongside Goombas due to their lack of specialized offensive capabilities, while Magikoopas are often given advisory roles due to their magical abilities and gift of foresight.

However, not all Koopas are allied with Bowser. Some Koopas, such as the Koopa Troopas of Koopa Village, live peacefully inside the borders of the Mushroom Kingdom, while others, such as Koopa_the_Quick in Super_Mario_64 and the Roving Racers in Super_Mario_Odyssey, simply hold no allegiance and operate independently.

Koopas in general are based on the Shellcreeper from Mario_Bros., as evident by various enemies being tentatively named and designed after Shellcreepers in development documents of Super_Mario_Bros._1.