Who was the first muadhin of Islam?

Hazrat Bilal called the first Azan of  Fajar prayer

First Azan was called out in 1 A.H

Bilal ibn Rabah is considered to have been the first muezzin, chosen by Hazrat Muhammad himself.

The Title of Bilal ibn Rabah: Sayyid al-Muʾaḏḏin

Bilal ibn Rabah Born: 580 AD, Mecca, Saudi Arabia

Bilal ibn Rabah Died: on March 2, 640 AD, in Damascus, Syria

Bilal ibn Rabah’s Place of burial: Bab el Saghir Cemetery, Damascus, Syria