He was born near Todi, Umbria, in a place now named after him (i.e. Pian di San Martino). St. Martin acted as the papal apocrisiarius or legate at Constantinople and was held in high repute for his learning and virtue. He succeeded Pope Theodore I in July 649. He was the only pope during the Byzantine Papacy whose election was not approved by a iussio from Constantinople.
St. Martin I conduced the Lateran Council which condemned the patriach of Constantinople for Monothelitism, which heretically claimed that Christ had no human will. This put the holy saint in opposition to Emperor Constans II who had him arrested and tortured. Paul, Patriarch of Constantinople, repented of his stance which saved Martin from execution, but the pope died in the Crimean Peninsula soon after from damage done during his imprisonment. He is considered the last martyred pope.
O Eternal Shepherd, who appointed blessed Martin shepherd of the whole Church, let the prayers of this martyr and supreme pontiff move You to look with favor upon Your flock and to keep it under Your continual protection. Through our Lord . .