An expression used by astrologers that generally indicates the planet that rules the first house (also called the Rising Sign or Ascendant) of a horoscope chart. Some astrologers use a different definition, describing the Chart Ruler as the planet nearest the first house cusp, which is very close to the Ascendant.

No matter the definition, the effects of a Chart Ruler are often quite profound, and according to some are associated with one's physical appearance.