The South African government is releasing more than 14,000 prisoners to mark the anniversary of Nelson Mandela winning the country's first democratic elections in 1994.
It represents about 9% of the country's prison population.
Another 20,000 offenders, on probation or parole, will not return to prison.
Police Minister Nathi Mthethwa said violent criminals and those jailed for sexual, drug-related and weapons offenses will not be freed.
Prison overcrowding was being reduced from 34% over capacity to about 20%.
Since 1994, prisoners have been amnestied on several symbolic occasions.
