Principal may refer to:
Education
The head of an educational institution:
Law
- Principal (commercial law), a person who authorises an agent to act to create a legal relationship with a third party
- Principal (criminal law), one (or more) primary actor(s) in a criminal offense for which other actors may be criminally liable as accomplices, accessories or conspirators
Other uses
- Principal sum, the original amount of a debt or investment on which interest is calculated
- Organ stop on a pipe organ
- A musician in an orchestra who either plays the first part (wind instruments), or who sits in the first chair and leads a section (of string instruments) in playing the same part
- A performer in an opera or musical who takes a more or less prominent part in the action, and sings solo or in small ensembles
- Principal value, values along a chosen branch of a multivalued function
- Principal branch, a special selected branch of a multivalued function
- Principal ideal, in ring theory in mathematics, an ideal with a single generator, and the related concept of principal ideal domains
- The Cauchy Principal Value of an integral, in mathematics, a way of assigning a finite value to improper integrals that seem to diverge
- Principal (Civil Service) or Principal Officer, a senior management grade (now grade 7) in the British Civil Service and the Irish Civil Service
- A security principal is an entity that can be positively identified and verified via a technique known as Authentication
- Principal, Cape Verde, a village
- Principal Financial Group, a life insurance company traded on the NYSE