古典音乐是指根植于西方音乐传统（包括宗教音乐和世俗音乐）的艺术音乐，包含了从大约11世纪直至当代的广大时间范围。这一艺术传统的中坚时期通常被划定为从1550年到1900年的这段时间，又称共晓时期。

西方音乐记谱法除了为演奏者预设了一段音乐的音高、速度、拍子、节奏，其特别之处在于对细节的处理也进行了描述，例如即兴装饰音与力度变化，然而这些即兴装饰音通常是为了尚未精通即兴演奏艺术的初学者而写的，另一方面，力度变化在很多情况下没有标示，需要仰赖演奏者对音乐的内在了解去做诠释。与其他乐种一样，古典音乐在器乐方面有相当高度的发展，这与以歌曲为主的流行音乐形颇为不同。

Classical music is art music produced or rooted in the traditions of Western music, including both liturgical (religious) and secular music. While a similar term is also used to refer to the period from 1750 to 1820 (the Classical period), this article is about the broad span of time from roughly the 11th century to the present day, which includes the Classical period and various other periods. The central norms of this tradition became codified between 1550 and 1900, which is known as the common practice period. The major time divisions of classical music are as follows: the early music period, which includes the Medieval (500–1400) and the Renaissance (1400–1600) eras; the Common practice period, which includes the Baroque (1600–1750), Classical (1750–1820), and Romantic eras (1804–1910); and the 20th century (1901–2000) which includes the modern (1890–1930) that overlaps from the late 19th-century, the high modern (mid 20th-century), and contemporary or postmodern (1975–2015) eras.