HM Prison Swansea (Welsh: Carchar Abertawe EF) is a Category B/C men's prison, located in the Sandfields area of Swansea, Wales. The prison is operated by His Majesty's Prison Service.

Swansea is a Victorian prison built between 1845 and 1861 to replace former prison accommodation at Swansea Castle. Both male and female inmates were incarcerated there until 1922, at which point all females were transferred to Cardiff Prison.

A total of 15 judicial executions took place at Swansea prison between 1858 and 1958. All of the condemned prisoners were hanged for the crime of murder. Their names, ages and dates of execution are:

Note: The execution of Jones & Mackintosh in 1949 was notable for being a double hanging i.e. both condemned men were executed simultaneously, whilst standing together on the same gallows. Jones & Mackintosh had committed unrelated murders. Double executions were already rare in the UK and the practice ended in 1952.

The remains of all executed prisoners were buried in unmarked graves within the prison walls, as was customary.

In April 2002, an inspection report from His Majesty's Chief Inspector of Prisons condemned conditions for inmates at Swansea Prison. The report called on the prison to improve cleanliness and sanitation, particularly for vulnerable inmates who are housed away from other prisoners. The report also highlighted the lack of showers in all areas, which meant that not all inmates were able to shower every day. However the prison was praised for its rehabilitation of inmates.

Four months later, a survey of prison numbers revealed that HMP Swansea was Wales's most overcrowded prison, and one of the top five most densely populated in Britain. Statistics showed that Swansea was holding 145 more inmates than the 219 it should have been accommodating. Overcrowding has been an issue at the prison ever since.

Swansea is a Category B/C prison for adult males remanded into custody from the local courts, as well as convicted and sentenced prisoners.