Isis was the wife of Osiris and the mother of Horus in the central Egyptian Osiris myth.
Isis and Osiris were siblings as well as spouses within the Heliopolitan divine family, children of Geb and Nut. When Osiris was killed and dismembered by his brother Set, Isis searched for his remains with the help of Nephthys and other gods. Their restoration of his body became a mythical model for Egyptian funerary rites and mummification.
After reviving or reconstituting Osiris, Isis conceived Horus, who was destined to inherit his father’s kingship. In developed versions of the story, she raised and protected the young Horus in the Nile Delta while hiding him from Set and guarding him against snakes, scorpions, and illness.
Hathor can cause confusion because some older or alternative traditions identify her with Horus’s mother, and the name “Horus” covers more than one ancient deity. Nevertheless, in the Osiris cycle presented by this question, Isis is the single canonical answer. Her devotion also made her an enduring symbol of motherhood, magic, protection, and royal legitimacy.