In economics, the free-rider problem is a type of market failure that occurs when those who benefit from resources, public goods and common pool resources do not pay for them or under-pay. Free riders may overuse common pool resources by not paying for them, neither directly through fees or tolls, nor indirectly through taxes. Consequently, the common pool resource may be under-produced, overused, or degraded. Additionally, despite evidence that people tend to be cooperative by nature (a prosocial behaviour), the presence of free-riders has been shown to cause cooperation to deteriorate, perpetuating the free rider problem.

In social science, the free-rider problem is the question of how to limit free riding and its negative effects in these situations, such as the free-rider problem of when property rights are not clearly defined and imposed. The free-rider problem is common with public goods which are non-excludable  and non-rivalrous. The non-excludability and non-rivalry of public goods results in there being little incentive for consumers to contribute to a collective resource as they enjoy its benefits as per the Tragedy of the commons.

A free rider may enjoy a non-excludable and non-rivalrous good such as a government -provided road system without contributing to paying for it. Another example is if a coastal town builds a lighthouse, ships from many regions and countries will benefit from it, even though they are not contributing to its costs, and are thus "free riding" on the navigation aid. A third example of non-excludable and non-rivalrous consumption would be a crowd watching fireworks. The number of viewers, whether they paid for the entertainment or not, does not diminish the fireworks as a resource. In each of these examples, the cost of excluding non-payers would be prohibitive, while the collective consumption of the resource does not decrease how much is available.

Although the term "free rider" was first used in economic theory of public goods, similar concepts have been applied to other contexts, including collective bargaining, antitrust law, psychology, political science, and vaccines. For example, some individuals in a team or community may reduce their contributions or performance if they believe that one or more other members of the group may free ride.

The economic free-rider problem is equally pertinent within the realm of global politics, often presenting challenges in international cooperation and collective action. In global politics, states are confronted with scenarios where certain actors reap the benefits of collective goods or actions without bearing the costs or contributing to the efforts required to achieve these shared objectives. This phenomenon creates imbalances and hampers cooperative endeavors, particularly in addressing transnational challenges like climate change, global security, or humanitarian crises. For instance, in discussions on climate change mitigation, countries with lesser contributions to greenhouse gas emissions might still benefit from global efforts to reduce emissions, enjoying a stable climate without proportionally shouldering the costs of emission reductions. This creates a disparity between states' contributions and their gains, leading to challenges in negotiating and implementing effective international agreements. The economic free-rider problem's manifestation in global politics underscores the complexities and obstacles encountered in fostering collective action and equitable burden-sharing among nations to address pressing global issues."

Without selective incentives to motivate active participation, collective action is unlikely to occur even when large groups of people with common interests exist. The book notes that large groups will face relatively high costs when attempting to organize for collective action while small groups will face relatively low costs, and individuals in large groups will gain marginally less per capita. Hence, in the absence of selective incentives, the incentive for group action diminishes as group size increases, so that large groups are less able to act in their common interest than small ones.