"Torturers, and their superiors, need to hear the following message loud and clear: however powerful you are today, there is a strong chance that sooner or later you will be held to account for your inhumanity," Pillay said.
"Torture is an extremely serious crime, and in certain circumstances can amount to a war crime, a crime against humanity or genocide," she added in a statement to mark Saturday’s International Day for the Victims of Torture.
"I am concerned, however, that some states rigidly maintain amnesties that save torturers from being brought to justice, even though the regimes that employed them are long gone.
That often, as a result, denied their victims reparations.
The UN human rights chief noted that more people were being prosecuted for torture every year, including recent prosecutions in Chile and Argentina for cases dating back to the 1970s and 1980s.
"There is one aspect of all this that should cause even the most ruthless and self-confident torturers to stop and think: in time, all regimes change, including the most entrenched and despotic.
"So even those who think their immunity from justice is ironclad can — and I hope increasingly will– eventually find them in court," Pillay added.