Russell Brand Behind Bars After Rape Conviction, Judge Denies Bail

7:30 AM PT -- Russell Brand has officially been denied bail and will remain behind bars until Monday, when he's scheduled to be sentenced.

Russell Brand has gone from the courtroom to a holding cell ... after being found guilty of rape and sexual assault Thursday, with a judge warning he's facing serious prison time.

The actor and comedian was taken down to the cells at London's Southwark Crown Court while awaiting arguments over whether he'll be granted bail ... with a hearing scheduled for 3 PM local time.

Brand reportedly showed no emotion as he was led away by court officers ... loudly telling the judge, "Yes, my lord."

But the judge didn't sound too optimistic about Brand's chances of walking free ... telling him a "significant custodial term" was inevitable following his conviction.

Justice Bennathan said his current view was that Brand should be remanded into custody ... meaning he could remain behind bars as he awaits sentencing.

As TMZ reported ... Brand was convicted of one count of rape and three counts of sexual assault following a weeks-long trial involving allegations from six women.

Russell was declared not guilty of indecent assault ... with the judge giving a directed verdict. He was recharged with attempted indecent assault and acquitted. He was also found not guilty on two other counts of rape.

The maximum sentence for rape in the UK is life imprisonment ... though the actual punishment varies depending on the circumstances of the case.