Yin or YIN may refer to:
- the dark force in the yin and yang from traditional Chinese philosophy and medicine
- the Moon in this philosophy
- Yīn (surname) (), a Chinese surname
- Yīn (surname 陰), a Chinese surname
- Yǐn (surname) (), a Chinese surname
- Yìn (surname) (), a Chinese surname
- Shang dynasty, also known as the Yin dynasty
- Yinxu or Yin, the Shang dynasty capital now in ruins
- Yin (Five Dynasties period), a short-lived kingdom during China's Five Dynasties and Ten Kingdoms period
- Yin Mountains, a mountain range in Inner Mongolia and Hebei province in China
- Yin (, yǐn), an office of early China sometimes equivalent to prime minister and sometimes to governor
- Prime minister (Chu State), known in Chinese as Lingyin.
- YIN, the IATA code for Yining Airport, Xinjiang, China