A nonprofit organization (NPO) or non-profit organization is a legal entity organized and operated for a collective, public or social benefit, in contrast to an entity that operates as a business aiming to generate a profit for its owners. Nonprofits are subject to the non-distribution constraint, which means that any revenues that exceed expenses must be committed to the organizations purpose, not taken by private parties. Nonprofits can have members, but many do not. The nonprofit may also be a trust or association of members. The organization may be controlled by its members who elect the board of directors, board of governors or board of trustees. A nonprofit may have a delegate structure to allow for the representation of groups or corporations as members. Alternatively, it may be a non-membership organization and the board of directors may elect its own successors.

Nonprofit organizations are often used for trusts, cooperatives, advocacy, charity, environmental and religious groups. They are designed to better their community by facilitating donations and grants into programs. Nonprofits may receive funding from individuals, corporations, government entities, or other entities. To qualify as a nonprofit, the entity must serve the public good, meet filing requirements, be established as a 501(c)(3) or similar-type organization, and avoid engaging in certain types of activities. Nonprofit organizations are often called NPOs or 501(c)(3) organizations based on the section of the tax code that permits them to operate.

Nonprofit organizations include churches, public schools, public charities, public clinics and hospitals, amateur sports organizations, political organizations, legal aid societies, volunteer services, organizations, labor unions, professional associations, research institutes, museums, and some governmental agencies. Nonprofit entities are organized under state law. For nonprofit corporations, some states have adopted the Revised Model Nonprofit Corporation Act (1986). For non-profit associations, a few states have adopted the Uniform Unincorporated Nonprofit Association Act.

The terms nonprofit organization (NPO) and not-for-profit organization (NFPO) are sometimes used interchangeably. There are, however, key distinctions between the two types of enterprise. A key one is their purpose. Nonprofits must offer some social benefit and provide goods or services. Not-for-profits need not have such an orientation and may exist simply to serve their membership rather than society at large.