Syntactic ambiguity, also called structural ambiguity, amphiboly or amphibology, is a situation where a sentence may be interpreted in more than one way due to ambiguous sentence structure.

Syntactic ambiguity arises not from the range of meanings of single words, but from the relationship between the words and clauses of a sentence, and the sentence structure underlying the word order therein. In other words, a sentence is syntactically ambiguous when a reader or listener can reasonably interpret one sentence as having more than one possible structure.

In legal disputes, courts may be asked to interpret the meaning of syntactic ambiguities in statutes or contracts. In some instances, arguments asserting highly unlikely interpretations have been deemed frivolous. A set of possible parse trees for an ambiguous sentence is called a parse forest. The process of resolving syntactic ambiguity is called syntactic disambiguation.