Galla Placidia in Harpers Dictionary

Placidia, daughter of the preceding by Theodosius. When Alaric took Rome in A.D. 410, she fell into his hands, and four years later was married by Ataulphus, king of the Goths. Upon his death she was returned to her country, and in 417 married Constantius III., by whom she had the emperor Valentinian III. During the minority of her son she was regent of the Western Empire, dying about the year 450. See Gibbon, Decline and Fall, chapters xxxi., xxxiii., xxxv.