From the LCMS website:
A native of North Africa, Monica (A.D. 333–387) was the devoted mother of Saint Augustine. Throughout her life she sought the spiritual welfare of her children, especially that of her brilliant son, Augustine. Widowed at a young age, she devoted herself to her family, praying many years for Augustine’s conversion. When Augustine left North Africa to go to Italy, she followed him to Rome and then to Milan. There she had the joy of witnessing her son’s conversion to the Christian faith. Weakened by her travels, Monica died at Ostia, Italy on the journey she had hoped would take her back to her native Africa. On some church year calendars, Monica is remembered on May 4.