A composer is a person who writes music. The term refers particularly to someone who writes music in some type of musical notation, thus allowing others to perform the music. This distinguishes the composer from a musician who improvises. However, a person may be called a composer without creating music in documentary form, since not all musical genres rely on written notation. In this context, the composer is the originator of the music, and usually its first performer. Later performers then repeat the musical composition they have heard.

The level of distinction between composers and other musicians also varies, which affects issues such as copyright and the deference given to individual interpretations of a particular piece of music. For example, in the development of classical music in Europe, the function of composing music initially had no greater importance than the function of performing music. The preservation of individual compositions received little attention, and musicians generally had no qualms about modifying compositions for performance. Over time, however, the written notation of the composer has come to be treated as strict instructions, from which performers should not deviate without good reason. This notion is often seen as a purist one.

The term "composer" is often used specifically to mean a composer in the Western tradition of classical music. In popular and folk music, the composer is typically called a songwriter (since the music generally takes the form of a song), and composers of jazz are often referred to as jazz writers.

Lists of composers

• List of composers
• List of opera composers
• List of uncategorized composers
• List of soundtrack composers

By style, time period, or technique

• List of classical music composers
• List of 20th century classical composers
• List of 21st century classical composers
• List of modernist composers

By nationality, culture, or identity

Category

• Composers
• Music occupations
• Classical music