Ruth was a Moabitess who married into the tribe of Judah and became king David’s great-grandmother. She is, therefore, an ancestress of the Lord Jesus Christ.
Her story is told in the book of Ruth.
Matthew 1:5 NKJV Salmon begot Boaz by Rahab, Boaz begot Obed by Ruth, Obed begot Jesse, 6 and Jesse begot David the king.
I hope you find this helpful.