Mousawi is the family name of thousands of people all around the world, mainly in the Middle East. They all share the same ancestor Imam Mousa Al Kadhim, hence the name Mousawi.

Mousa Al Kadhim is a descendant and a successor of the prophet Mohammed (pbuh) through his daughter Fatima Al Zahra and her husband Imam Ali bin Abi Talib (Amir Al Mumineen), who was the Prophet's paternal first cousin and the fourth caliph of Islam.

Ali and Fatima had two sons: Al Hassan and Al Hussein. The direct descendants of their eldest son, Al Hassan, are known as "Sharifs" (Nobles); while the direct descendants of Al Hussein are called "Sayyids" (Lords). Mousa Al Kadhim is a descendant of Al Hussein (Al Hussein's grand grand grandson), therefore the Mousawis are Sayids.