Sweyn Estridsson Ulfsson was King of Denmark from 1047 until his death in 1076. He was the son of Ulf Thorgilsson and Estrid Svendsdatter, and the grandson of Sweyn Forkbeard through his mother's line. He was married at least two times, and fathered 20 children or more out of wedlock, including the five future kings Harald Hen, Canute the Saint, Oluf Hunger, Eric Evergood, and Niels.

Ulf Thorgilsson, commonly known as Ulf Jarl or Earl Ulf, was a Danish jarl of Skåne and regent of Denmark. Ulf was the son of Thorgil Sprakling and the father of King Sweyn II of Denmark and thus the progenitor of the House of Estridsen, which would rule Denmark from 1047 to 1375, which was also sometimes, specially in Swedish sources, referred to as the Ulfinger dynasty to honor him.