Adelaide was born around 931 to King Rudolf II of Burgundy and his queen Bertha of Swabia. At age 6, on the death of her father in 937, she was betrothed (and at age 16, in 947, married) to Lothair II of Italy — the son of Hugh of Provence and king of Italy.
Lothair II died (probably poisoned) in November 950; his successor Berengar II of Ivrea usurped the Italian throne and attempted to compel Adelaide to marry his son Adalbert. Refusing, she was imprisoned in 951 by Berengar in the fortress of Garda — but miraculously escaped (per tradition, by digging through the castle floor with the help of her chaplain).
From hiding she appealed to the German king Otto I — who invaded Italy, defeated Berengar, and married Adelaide himself in 951 at Pavia. The marriage united the German and Italian royal traditions; on Christmas Day 962, the couple were crowned by Pope John XII as Holy Roman Emperor and Empress — the beginning of the thousand-year Holy Roman Empire that would continue until 1806.
Adelaide and Otto I produced four children: Henry, Bruno (both died in infancy), Mathilda (abbess of Quedlinburg), and Otto II (future emperor, 973–983).
On Otto I's death in 973, Otto II succeeded as emperor (with his Byzantine-princess wife Theophanu); Adelaide clashed with her daughter-in-law and was exiled from court. On Otto II's sudden death in 983 (at the age of 28), Adelaide returned as co-regent (with Theophanu) for her three-year-old grandson Otto III. On Theophanu's death in 991, Adelaide ruled as sole regent until Otto III's majority in 994 — making her the uniquely the empress-regent for three generations (queen-consort of Otto I, queen-mother of Otto II, queen-regent for Otto III).
In 991 she founded the monastery of Seltz in Alsace as her personal retreat; she died there on December 16, 999, having lived through and shaped the Ottonian Catholic-imperial settlement of central and southern Europe. Pope Urban II canonized her in 1097.