黏着语（Agglutinative language），为综合语（synthetic language）的一种，具有词形变化的一种语言类型。黏着语透过在名词、动词等词根粘加上不同的词尾来表达语法功能。

黏着语与同为综合语的屈折语的关键差别在于：黏着语的所有、或多数词缀仅表达一种意思或仅具有一种语法功能（例如日语的语尾修饰）。而屈折语一词缀之使用则往往是一通用的语法功能（例如印欧语系中常见的格、性等变化）。并且，大多状况中，黏着语较屈折语能不受限制地在词素加上更多词缀作为修饰语。 但必须注意的是，在大多数案例中，黏着语和屈折语之间的界限并不明显，因此可将黏着语和屈折语之间的关系视为一个光谱连续体或混和体。

An agglutinative language is a type of synthetic language with morphology that primarily uses agglutination: words may contain different morphemes to determine their meaning, but each of these morphemes (including stems and affixes) remains in every aspect unchanged after their union, thus resulting in generally easier deducible word meanings if compared to fusional languages, which allow modifications in either or both the phonetics or spelling of one or more morphemes within a word, generally for shortening the word on behalf of an easier pronunciation. The term was introduced by Wilhelm von Humboldt to classify languages from a morphological point of view. It is derived from the Latin verb agglutinare, which means "to glue together".