In J.R.R. Tolkien’s legendarium, nine Rings of Power were given to mortal Men.
The distribution is described in the verse about the Rings: three went to Elves, seven to Dwarves, nine to Men, and one ruling Ring was made for Sauron. Tolkien’s account presents the rings as instruments shaped by the history of the Second Age and the rise of Sauron.
The nine human ring-bearers eventually became the Nazgûl, also called the Ringwraiths or Black Riders. Their names are generally not given in Tolkien’s main narrative, although the Witch-king of Angmar is identified as their chief.
A common mix-up is to remember the three Elven Rings or the seven Dwarven Rings instead. The number nine specifically belongs to the gifts made to mortal Men, whose longer lives and power were twisted into servitude.