Portlaoise Prison (Irish: Príosún Phort Laoise) is a maximum security prison in Portlaoise, County Laois, Ireland. Until 1929 it was called the Maryborough Gaol. It should not be confused with the Midlands Prison, which is a newer, medium security prison directly beside it.The prison was built in the 1830s, making it one of the oldest still operating today in the Irish prison system.