The term “demigod”, evolved from the Latin semideus, can refer to a variety of lesser divine beings, but in contemporary Western use tends to refer mostly to the child of a god and a human. Greek mythology was full of these, the most notable being Heracles, Perseus, Theseus, and Achilles. Also fairly well known are the half-god, half-human heroes of the Mahabharata in Hindu mythology, though the term demigod is moreso used in India to refer to lesser gods. Jimmu, the legendary first Emperor of Japan, was also a demigod. But demigods pop up in a wide variety of places in mythology, including some where you might not expect them at all.
The Penobscot, a Native American tribe from modern-day Maine and Atlantic Canada and a part of the five-nation Wabanaki Confederacy, have a myth about Mount Katahdin (the highest mountain in Maine). In their tales, a powerful being called Pamola lived atop the mountain, a great bird with moose-like features. While sources tend to not call him a god, preferring terms like “spirit” instead, this is a typical bias when writing about Native American mythologies, and since he was incredibly powerful, had a luxurious home within the mountain that he would bid mortals visit, and was regularly sacrificed to, it’s fair to at least call him analogous to a god.
So one day, a young woman sought out Pamola, and he brought her to his home, married her, lived with her for a year, and got her pregnant, sending her home before the child, who was to be incredibly powerful, was born. The little boy, an authentic demigod, was said to have the power to strike someone dead simply by pointing at them. He was one hell of a hunter, which was nice for his mother and their community, but inevitably, one day he saw his mom’s friend coming, got excited, and pointed him out to her.
And so the wonder child became a pariah, and the community that loved him now fled from his sight. They then wanted the woman to get married (for some reason), even though she was already married to Pamola, and eventually she succumbed, remarrying. The night of the ceremony, she and her son disappeared forever, returning to Pamola’s home within the mountain.