字符实体引用(character entity reference), 是标记语言 SGML与HTML中对字符的一种转义串行表示, 通过文档类型描述(DTD)中预定义且明确声明的SGML命名实体的引用来描述Unicode字符. 其目的是对当前文档的编码方式不能包含的字符，提供一种转义表示。这种方法也被称作"实体引用"(entity references)甚至"实体"(entity), 虽然这种说法是不妥当的.

一个实体声明通过<!ENTITY name "value">DTD或XML语法来创建。实体声明中定义的名字可以在随后的XML中使用.

In SGML, HTML and XML documents, the logical constructs known as character data and attribute values consist of sequences of characters, in which each character can manifest directly (representing itself), or can be represented by a series of characters called a character reference, of which there are two types: a numeric character reference and a character entity reference. This article lists the character entity references that are valid in HTML and XML documents.