The Norse god who is the father of the goddess Hel is Loki.
In the surviving mythological sources, Loki fathers Hel with the giantess Angrboða. Their other famous children are Fenrir, the monstrous wolf, and Jörmungandr, the Midgard Serpent. This family is central to the prophecies surrounding Ragnarök.
Hel is both a female supernatural being and the name commonly used for the realm she rules. The gods learn that Angrboða’s children are being raised in Jötunheimr and recognize them as threats. Odin eventually sends Hel to govern the dead who do not die in battle, while Fenrir and Jörmungandr remain tied to the catastrophe to come.
The answer is sometimes confused because popular culture gives Loki different family relationships, especially in Marvel adaptations. In Norse mythology, however, Hel is not Loki’s sister through Odin; she is his daughter. Loki’s parentage and nature are themselves unusual: his father is the jötunn Fárbauti, and his mother is usually named Laufey or Nál.