Mahlon (Hebrew: מַחְלוֹן Maḥlōn) and Chilion (כִּלְיוֹן Ḵilyōn) were two brothers mentioned in the Book of Ruth. They were the sons of Elimelech of the tribe of Judah and his wife Naomi. Together with their parents, they settled in the land of Moab during the period of the Israelite Judges. On foreign soil, Mahlon married the Moabite convertRuth (Ruth 4:10) while Kilion married the Moabite convert Orpah.
Elimelech and his sons all died in Moab, leaving Naomi, Ruth, and Orpah widowed. Ruth and Orpah did not bear Jewish children, too. The story in the book gives account, that Naomi plans to return to Israel, and tests her daughters-in-law. She gives them the advice to return to their mother's home, meaning, drastically violating Jewish Law and reverting to Moabite culture and idol worship.
While Orpah returns and leaves Judaism, Ruth chooses to stay with Naomi, thus proving her former conversion to be a real one. In Israel, Ruth then takes part in a levirate marriage, according to Jewish law. By marrying a relative of Mahlon's, she is doing an act which will ensure that Mahlon's paternal lineage is not forgotten. Any child she bears in the levirate marriage will be considered as if it were Mahlon's child. Actually, she marries a younger brother of Elimelech, Boaz, being the head of the Jewish Sanhedrin (Jewish high court) at that time. Her child, Obed (biologically Boaz's but counted as if Mahlon's), becomes the paternal grandfather of David ha-Melech (King David).