For the mathematical concept, see characterization (mathematics).

Characterization is the process of creating characters in fiction, often those who are different from and have different beliefs than the author. A writer can assume the point of view of a child, an older person, a member of the opposite gender, someone of another race or culture, or anyone who isn't like them in personality or otherwise.

Thorough characterization makes characters well-rounded and complex even though the writer may not be like the character or share his or her attitudes and beliefs. This allows for a sense of realism. For example, according to F.R. Leavis, Leo Tolstoy was the creator of some of the most complex and psychologically believable characters in fiction.

Characterization can involve developing a variety of aspects of a character, such as appearance, age, gender, educational level, vocation or occupation, financial status, marital status, hobbies, religious beliefs, ambitions, motivations, etc. Often these can be shown through the actions and language of the character, rather than by telling the reader directly.

In fan fiction, thorough characterization is not usually necessary since a writer is using characters already familiar to the reader. An exception is in stories set in alternative universes, which may significantly change the personalities of characters established by others, and directly revealing details may be necessary to avoid reader confusion or to warn the reader of settings he or she may not like.