Imam Muhammad at Taqi (April 12, 811 - November 27, 835) was the ninth Shia Imam. His given name was Muhammad bin Ali bin Musa.

Muhammad at Taqi was born in Medina to Ali ar Rida and a Nubian slave named Khaizuran. He was only nine when his father died, and as such, many doubed his ability to carry the Imamate. However, he held on to his position with the help of Al Ma'mun whose patronage proved valuble to the young Imam, and who brought him to live in Baghdad. Eventually, Muhammad would be married to Al Ma'mun's daughter, Umm al Fadl. During his time in Baghdad he was well known for posessing an amazing amount of knowledge, especially when considering his young age.

After living in Baghdad for a few years, Muhammad returned to Medina. Here, he found his relationship with his wife strained, and upon the death of Al Ma'mun, he saw his fortunes deteriorate. The sucessor to his father in law, was Al Ma'mun's half brother, al=Mu'tasm. With the new Abbasid ruler in power, Muhammad was no longer protected, and was not helped by the dislike that Al Mu'tasm had for the Imam.

Al Mu'tasm would call Muhammad at Taqi back to Baghdad where he hoped to convert him to the lavish lifestyle of the palace. Muhammad left his son Ali al Hadi with his mother in Medina and set out for Baghdad. He resided there for one more year, not influenced as al-Mu'tasm had hoped, rather becoming a well known scholar and popular in debates. Al Mu'tasm would grow tired of him, and Muhammad at Taqi would die suddenly, likely via poison on November 27, 835. He would be buried alongside his grandfather, Musa al Kazim at Kazmain.