Haham R. Shimon Agasi of Baghdad was born in 1852 to his father R. Aaron Agasi, a scion from a Persian family whose heads were appointed from the government as leaders of the entire Jewish community. He first studied in the Yeshiva that was founded by R. Abdallah Sumah, and subsequently at R. Yitzchak Sassoon, where he acquired most of his Torah and leadership skills.

R. Shimon was a close friend of the famous Ben Ish Chai, whom he later replaced as Chief Rabbi of Baghdad. He was known as a heavenly saint, a giant in Halacha and Kabbalah, who had heavenly powers to perform miracles, and who's blessings never returned empty. As Chief Rabbi of Baghdad he would not take a salary or any money from his congregants. He taught students, and many of the later Babylonian scholars were his disciples. His works Shem Me'Shimon Imrei Shimon and others are widely available. He wrote a kabbalistic work "Bnei Aaron" a commentary on the Shaar Hagilgulim of the Arizal edited by R. Chaim Vital, which he named after his son R. Aaron who passed on at a young age. He died on the eve of Tisha B'Av 1914, the day WWI broke out. The Turkish Ottoman government's decision to draft Jewish youth to the army prompted R. Agasi to hold a sermon at the time, which became famous as "The Sermon of Repentance."