St Therese's remains will spend a few hours in Wormwood Scrubs prison
The relics of the French Carmelite nun St Therese of Lisieux are being taken to Wormwood Scrubs jail later.
The relics have been on a month-long visit to England and Wales, which draws to a close this week.
Thousands of people have queued to see the casket containing bones from the Roman Catholic saint's thigh and foot.
They will visit the Anglican Chapel at Wormwood Scrubs in west London, where most of the 300 Catholic prisoners are expected to pay their respects.
St Therese - who died of tuberculosis in 1897 at the age of 24 - captured the imagination of Catholics for the simplicity and humility revealed in her autobiography.
She was described by Pope Pius X as the "greatest saint of modern times" and had said she would use her time in heaven to do good on earth.
As a result, many Catholics pray to her as a "bridge to God".
Her relics have attracted large crowds to churches and cathedrals - the relics are at Westminster Cathedral this week - but the tour's organisers said it was also important they should go to places where they could do good.
The BBC's religious affairs correspondent Robert Pigott said the visit to Wormwood Scrubs was confirmed shortly after inspectors found conditions at the jail had deteriorated and gang activity increased.