What was the divorce rate like in the medieval times?

The divorce rate was low among people of whom we have records. Important members of the nobility had to get permission of the Church to get a divorce because marriage required oaths and it was the right of the Church to release people from oaths. Among the nobility, inheritance and legitimacy were very important issues. The position of the Church was that the oaths were permanent unless there was some reason why their was some impediment at the time they were made. Reasons included consanguinity, meaning the couple were too closely related. But other reasons included that the match was arraigned or concluded when the parties were too young to use their own discretion on the matter.

It should be born in mind that during the Middle Ages, private marriage was a private matter. While the Church had teachings on the matter, it did not necessarily have any control. A couple of less than noble status made oaths to each other, and the marriage was done; there was no need for involvement of clergy or witnesses. The registration of the marriage with the local church was optional. Under the circumstances, divorce would not necessarily be an issue, if people wanted to separate, and we, as observers separated from the events by the centuries, would not be the wiser. So, the divorce rate could have been high in some places and times, and we would not necessarily have any way to know.

There are links below on divorce and marriage.