“Holier than thou” is a phrase used to describe someone who acts superior to others or is perceived to act that way. Typically, “holier than thou” refers to an attitude that places an individual above others on a moralistic level. Although no one is perfect, a “holier than thou” outlook might lead a person to be quick to point out other people's flaws but rarely notice his or her own. A “holier than thou” attitude often refers to someone so pious and devout in their beliefs that they judge others, which many people consider to be exactly the opposite of the biblical warning “judge not.”

The exact origin of this phrase is unknown. It is sometimes presumed to have originated from a biblical passage in Isaiah 65:5, the King James Version translation of which states: “come not near me, for I am holier than thou.” Regardless of its origin, the phrase didn't come into common usage in the English language until the 20th century.

The word “thou” originates from Old English. Although is used as an ordinary pronoun meaning “you,” it was once used in certain Bible translations to refer exclusively to God. Most often, the word “thou” was capitalized when referring to God. When examining the etymology of the word “thou” and its usage as a reference to God, the phrase “holier than thou” might be interpreted to mean putting oneself above God.

The attitude of the biblical Pharisees might be interpreted as “holier than thou.” The Pharisees were a group of religious leaders who were very devout in their beliefs. According to the books of the New Testament, the Pharisees adhered so strictly to religious laws that they opposed Jesus doing good works on the sabbath. In so doing, their “holier than thou” attitude was said to have been a transgression of the law because in their self-righteousness, they placed themselves above God.