Trainer may refer to:

• An aircraft used for training pilots
• A padded sports shoe ("trainer" is used commonly in British English where sneaker would be used in American English). The term "trainer" derives from "training shoe".
• A person who is responsible for preparing a horse for races.
• A person who guides another in developing physical fitness.
• A trainer (business) who instructs a person or persons on a particular subject within a formal curiculum or other educational process or method; usually in a business context.
• A hack of a ROM image that adds in extra options, usually to make the game easier.
• An Athletic trainer is one who provides medical assistance to athletes or other physically active individuals. It is improper to refer to an Athletic Trainer as 'Trainer.'