Wikipedia
Neithhotep (also written Neith-hotep) was an Ancient Egyptian queen consort living and ruling during the early 1st dynasty. She was once thought to be a male ruler: Her outstandingly large mastaba and the royal serekh ensnaring her name on several seal impressions led Egyptologists and Historians to the erroneous believe that she might have been a yet unknown king.
As the understanding of early Egyptian writings developed, scholars learned that Neithhotep was in fact a woman of extraordinary rank. Along with this realization, scholars viewed her now as the wife of king Narmer and mother of Hor-Aha. But according to newest discoveries, Neithhotep was in fact the spouse of Hor-Aha and the motherly co-regent of king Djer. She was thus maybe the first known female pharaoh of Egypt.