Russell Brand is expected to be sentenced to prison time Monday for raping and sexually assaulting 4 females — and if he does end up spending time behind bars, the actor will likely undergo therapy to help rehabilitate him, according to a law enforcement source.

The source — a member of London’s Metropolitan Police, the agency that investigated Brand — tells TMZ … if the judge on Monday sentences Russell to prison, then Russell will likely be transferred to a correctional facility specializing in housing sex offenders.

We’re told that, within a week, Russell will receive a psychiatric assessment by a mental health professional. Based on that assessment, mental health professionals will develop a “care plan” specifically tailored to his needs, and he will be assigned mandatory sexual therapy programs, our source says.

We’re told the programs are designed to try to rehabilitate him, so he can eventually assimilate back into society if he does not get a life sentence.

As you know, a jury found Russell guilty of one count of rape and three counts of sexual assault following a 4-week trial at Southwark Crown Court in London.