Who is the oldest prisoner In the planet?

Number 6.

Hard to say who, because there isn’t a central database. But there are prisoners in the US that are in their 80s and 90s, mostly with life sentences or on death row.

And there isn’t a rule or a law or a treaty governing an upper age limit for prisoners.

The oldest living person in North Korea.

One area that has jailed the elderly is when one of a couple is ill and the other ends the life of the ill partner. They are often the caregiver. The sickly person states, writes, (etc) they want to be ‘free’ ; an overdose, an act of ending life, even if it was assisted end of life suicide. The remaining partner is arrested by the mere fact they were present or could have prevented any actions that the ill may have taken. They have recieved jail sentences for enough time, they will not survive if already elderly. The lawyer who represented Jack Kevorkian MD, has represented some who were charged, due to being present and not preventing actions bringing death.
If they commit murder/kill the ill, they are charged with murder. Fatigue of caregiving is not taken into effect in judgement.
They go in, and others having done worse, get out early. Go figure.

Carlos Tapia-Ponce is 94

Everyone is a prisoner of his own body and of this world.
So the oldest prisoner alive today is therefore Yasutaro Koide at 112 years.

Women.
They have lived subserviant for centuries.