Prison overcrowding is when the demand for space in prisons in a jurisdiction exceeds the capacity for prisoners in the place. Prison overcrowding can occur when the rate at which people are incarcerated exceeds the rate at which other prisoners are released or die, thereby freeing up prison space.
At the end of 2010, United States state and federal correctional facilities housed over 1.6 million inmates. At least seven states are currently at 25% over capacity with the highest being Alabama at 196% and closely followed by Illinois at 144% above maximum capacity. Nineteen states in total are operating above maximum capacity. In 2007, California declared a "state of emergency" with regard to overcrowded prisons. 
Operating prisons over maximum capacity is expensive, and inconvenient and dangerous for both prisoners and employees. Possible problems caused by prison overcrowding include:
- Worsening of prison conditions such as sanitation and failure of basic services such as health care
- Spread of diseases within prisons
- Stress among inmates and staff
- Increased risk of violence and prison riots
Some of the solutions to prison overcrowding focus on increasing prison capacity. This includes the construction of new prisons, and the conversion of space within existing facilities that has been used for other purposes into prison space.
Other solutions that have been employed involve keeping offenders, particularly those who commit non-violent or less violent offenses, out of prison. Alternate forms of sentencing are used, including probation, community service, restitution, diversion programs, and house arrest. Additionally, inmates may become eligible for early release from parole and other credits.
- "Tackling Prison Overcrowding: Build More Prisons? Sentence Fewer Offenders? - Google Books". Books.google.com. 2007-08-28. Retrieved 2013-10-13.
- "Prison Overcrowding State of Emergency Proclamation - CA.Gov". Gov.ca.gov. Retrieved 2014-05-19.
- "California to Address Prison Overcrowding With Giant Building Program - New York Times". nytimes.com. 2007-04-27. Retrieved 2014-05-19.
- "Prisons: Today and Tomorrow - Google Books". Books.google.com. Retrieved 2013-10-13.