Boaz was a landowner of Bethlehem, a kinsman of Naomi's late husband, who married Ruth the Moabitess and became an ancestor of King David.
Ruth 2:1 in the King James Version reads:
And Naomi had a kinsman of her husband’s, a mighty man of wealth, of the family of Elimelech; and his name was Boaz.
The verse introduces Boaz at the opening of Ruth 2. Read it in context at Ruth 2:1, or the full chapter at Ruth 2. Encyclopedia entry: en.wikipedia.org/wiki/Boaz.