Sadr al-Din Sadr (Arabic: صدر الدين الصدر) (died 1954) was the father of Musa as-Sadr (disappeared in Libya in 1978) and the grandson of the Grand Ayatollah Sadr-eddine bin Saleh after whom the Sadr family of well-known scholars of Twelver Shi'a Islam has been named.
He is the second son of Sayyed Grand Ayatollah Ismail as-Sadr (d.1920). He was born in what is today Iraq to Lebanese parents and led a progressive religious group there. He then migrated to Khorasan where he married the daughter of Grand Ayatollah Hussein al-Qummi. Then he left to the Shia center of learning (hawzayi'ilmī) in Qom, Iran, where he became a renowned Grand Ayatollah. He died in 1954 in Iran.