Red hat (or Red Hat) has several possible meanings:

• Within the Roman Catholic Church, red hat refers to the appointment of a Cardinal, a senior Prince of the Church who is a member of the electoral college that chooses the Pope. A person on being appointed to the cardinalate is said to have received the red hat or cardinal's biretta.

• Red Hat, Inc. is one of the largest and most recognized companies dedicated to open source software.
  • Red Hat Linux is a Linux distribution, which was one of the most popular. It is assembled by Red Hat.
  • Red Hat Enterprise Linux is a Linux distribution created by Red Hat and targeted toward the business market.

• In Tibetan Buddhism successors to the first Shamarpa are known as the Red Hat lamas.

• In the 1985 book Six Thinking Hats by Edward De Bono, the red hat symbolizes opinion and emotion.

• The Red Hat Society, Inc. is a women's organization whose full members, who must be over 50 years old, wear red hats and purple dresses. Members are often called "Red Hatters."