A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and regulation ranging from local community-based groups to statewide government monopolies.

Public utilities are meant to supply goods and services that are considered essential; water, gas, electricity, telephone, waste disposal, and other communication systems represent much of the public utility market. The transmission lines used in the transportation of electricity, or natural gas pipelines, have natural monopoly characteristics. A monopoly can occur when it finds the best way to minimize its costs through economies of scale to the point where other companies cannot compete with it. If the infrastructure already exists in a given area, minimal benefit is gained through competing. In other words, these industries are characterized by economies of scale in production. Though it can be mentioned that these natural monopolies are handled or watched by a public utilities commission, or an institution that represents the government.

There are many different types of public utilities. Some, especially large companies, offer multiple products, such as electricity and natural gas. Other companies specialize in one specific product, such as water. Modern public utilities may also be partially (or completely) sourced from clean and renewable energy in order to produce sustainable electricity. Of these, wind turbines and solar panels are those used most frequently.

Whether broadband internet access should be a public utility is a question that was being discussed with the rise of internet usage. This is a question that was being asked due to the telephone service being considered a public utility. Since arguably broadband internet access has taken over telephone service, perhaps it should be a public utility. The Federal Communications Commission (FCC) in the United States in 2015 made their stance on this issue clear. Due to the telephone service having been considered a public utility, the FCC made broadband internet access a public utility in the United States.

Public utilities have historically been considered to be a natural monopoly. This school of thought holds that the most cost-efficient way of doing business is through a single firm because these are capital-intensive businesses with unusually large economies of scale and high fixed costs associated with building and operating the infrastructure, e.g. power plants, telephone lines and water treatment facilities. However, over the past several decades, traditional public utilities' monopoly position has eroded. For instance, wholesale electricity generation markets, electric transmission networks, electricity retailing and customer choice, telecommunications, some types of public transit and postal services have become competitive in some countries and the trend towards liberalization, deregulation and privatization of public utilities is growing. However, the infrastructure used to distribute most utility products and services has remained largely monopolistic.^{[citation needed]}

Key players in the public utility sector include:

Public utilities must pursue the following objective given the social responsibility their services attribute to them:

The management of public utilities continues to be important for local and general governments. By creating, expanding, and improving upon public utilities, a governmental body may attempt to improve its image or attract investment. Traditionally, public services have been provided by public legal entities, which operate much like corporations, but differ in that profit is not necessary for a functional business. A significant factor in government ownership has been to reduce the risk that an activity, if left to private initiative, may be considered not sufficiently profitable and neglected. Many utilities are essential for human life, national defense, or commerce, and the risk of public harm with mismanagement is considerably greater than with other goods. The principle of universality of utilities maintains that these services are best owned by, and operating for, the public. The government and the society itself would like to see these services being economically accessible to all or most of the population. Furthermore, other economic reasons based the idea: public services need huge investments in infrastructures, crucial for competitiveness but with a slow return of capital; last, technical difficulties can occur in the management of plurality of networks, example in the city subsoil.