A private prison is a detention center that is managed by a private enterprise, also called a for-profit enterprise. Most prisons are public prisons. A private prison differs from a public prison because a private prison is not operated by the government. Instead, the government pays a private enterprise to run the prison.

The earliest known form of prison privatization in the United States took place after the Civil War, although that particular system shared little with the modern private prison. The system was known as convict leasing. Essentially, private enterprises, such as farms or businesses, rented prisoners from federal and state governments. The prisoners would then provide labor for the private enterprises as if they were employees.

The topic of private prisons is a controversial one. Opponents of prison privatization argue that for-profit companies should not be in charge of inmates because they'll have a higher probability of being mistreated and abused. Additionally, opponents of private prisons argue that by privatizing prisons, companies are essentially making money when citizens go to jail. The longer they stay in jail, the more money the enterprise will make. Therefore, opponents say, the private prison industry will contribute to lobbying for harsher sentencing in order to serve their financial interests.

Proponents of the private prison industry argue that governments waste money on inefficient jails and detention centers and that the system should be left up to private enterprise. A private enterprise, it is argued, will have incentive to be more efficient in order to make more money. This also can create jobs and result in economic growth. This efficiency can benefit the government, and therefore the citizens, because less government money is spent to keep a certain number of prisoners incarcerated.

The number of prisons that are private represents a small minority. For example, as of 2010, there were approximately 2 million prisoners in the U.S., including those in state penitentiaries, local jails and federal prisons, but only about 100,000 of those were in private prisons. There were fewer than 300 private prisons in the U.S. as of 2010.