Instead, they will be kept at county jails as part of a plan to cut costs and reduce prison population.
It's the most radical change in the prison system in decades.
Some prosecutors and county sheriffs predict that the so-called "prison realignment" will lead to rising crime and other dire outcomes.
Realignment means judges will no longer sentence non-violent, lower-level offenders to state prison for crimes such as burglary, grand theft, counterfeiting and drug possession for sale. Instead, nearly 26,000 convicts who would previously have gone to state prison are expected to serve their time in county jails where, proponents say, they will be closer to home, jobs and rehabilitation programs and so will be less likely to commit new crimes after they are released.
L.A. County alone is expecting 10,000 extra inmates or people in probation in the first year alone.
Los Angeles County Sheriff Lee Baca, who runs the nation's largest jail system, has said he has 4,500 spare beds and is confident he can handle - at least initially - the influx of new inmates.
Gov. Jerry Brown says this is the most viable plan, given the state's overcrowded prison system.
"It's bold, it's difficult and it will continuously change as we learn from experience, but we can't sit still and let the courts release 30,000 serious prisoners," Brown said.
The new plan doesn't affect inmates in prison today, but rather applies to those convicted after this week.
Those convicted of sex crimes or violent offenses will continue to be sentenced to state prison.
While the length of sentences is to remain the same, jails in many counties are overcrowded and release inmates after they have served a fraction of their time. That dynamic could lead to more inmates being released early, as counties cope with the influx expected to peak over the next four years.
The Associated Press contributed to this report.