Xi Wang Mu is the highest ranking and most powerful female deity in Chinese mythology, said to be without beginning, and without end. She is the personification of the female Yin (chaos), she protects/presides over all women, female deities, marriage, fertility, and longevity. She takes care of the Immortal Peach Garden in Heaven where the Peaches of Immortality grow (yielding fruit once every 3,000 years). She is known by many names, most commonly in English, perhaps, is the Queen Mother of the West.
Her history is extremely complicated. The first known records of her are in oracle bone inscriptions and date back to the Shang dynasty (商朝 shāng cháo) between 1766 and 1122 BCE, and speak of sacrifices being made in her name. The first detailed description of Xi Wang Mu can be found in the Classic of Mountains and Seas (山海经 shān hǎi jīng), where she is described in a fashion that that couldn’t be further from her current day image; a part-human, part-beast deity, with a feral air about her:
又西北三百五十里，曰玉山，是西王母所居也。西王母其状如人，豹尾虎齿而善啸，蓬发戴胜，是司天之厉及五残。yòu xī běi sān bǎi wǔ shí lǐ, yuē yù shān, shì xī wáng mǔ suǒ jū yě. Xī wáng mǔ qí zhuàng rú rén, bào wěi hǔ chǐ ér shàn xiào, péng fā dài shèng, shì sī tiān zhī lì jí wǔ cán.
“Another 350 leagues to the northwest lies Yu Mountain. Xi Wang Mu lives on this mountain. Xi Wang Mu looks like a human, but with a leopards tail and tiger teeth. She enjoys (or, “is good at”) howling, and wears jewels in her tangled hair. She governs the Sky Calamities (天之厉tiān zhī lì) and the Five Atrocities (五残 wǔ cán).”