Co-operation refers to the practice of people or greater entities working in common with commonly agreed-upon goals and possibly methods, instead of working separately in competition.

Cooperation is the antithesis of competition, however, the need or desire to compete with others is a very common impetus that movitates individuals to organize into a group and cooperate with each other in order to form a stronger competitive force.

Co-operation in many areas such as, farming and housing may be in the form of a co-operative or, alternately, in the form of a conventional business.

Many people support cooperation as the ideal form of management of human affairs. In terms of individuals obtaining goods and services, rather than resorting to theft or confiscation, they may cooperate by trading with each other or by altruistic sharing.

Certain forms of co-operation are illegal in some jurisdictions because they alter the nature of access by others to economic or other resources. Thus, co-operation in the form of cartels or price-fixing may be illegal.

Even if all members of a group would benefit if all cooperate, individual self-interest may not favor cooperation. The prisoner's dilemma codifies this problem and has been the subject of much research, both theoretical and experimental. Results from experimental economics show that humans often act more cooperatively than strict self-interest would seem to dictate.

One reason for this may be that if the prisoner's dilemma situation is repeated (see iterated prisoner's dilemma), it allows non-cooperation to be punished more, and cooperation to be rewarded more, than the single-shot version of the problem would suggest. It has been suggested that this is one reason for the evolution of complex emotional and social behavior in higher animals.