A fusional language is a type of synthetic language, distinguished from agglutinative languages by its tendency to "squish together" many morphemes in a way which can be difficult to segment.

The canonical examples of fusional languages are Latin and German, with Dutch as a close follow-up. Most European languages are relatively fusional.

A good illustration of fusionality in language is the Latin word amo, "I love". The ending -o denotes indicative mood, active voice, first person, singular, present tense. Changing any of these features requires replacement of the suffix -o with something else.