Structural linguistics, or structuralism, in linguistics, denotes schools or theories in which language is conceived as a self-contained, self-regulating semiotic system whose elements are defined by their relationship to other elements within the system. It is derived from the work of Swiss linguist Ferdinand de Saussure and is part of the overall approach of structuralism. Saussure's Course in General Linguistics, published posthumously in 1916, stressed examining language as a dynamic system of interconnected units. Saussure is also known for introducing several basic dimensions of semiotic analysis that are still important today. Two of these are his key methods of syntagmatic and paradigmatic analysis, which define units syntactically and lexically, respectively, according to their contrast with the other units in the system. Other key features of structuralism are the focus on systematic phenomena, the primacy of an idealized form over actual speech data, the priority of linguistic form over meaning, the marginalization of written language, and the connection of linguistic structure to broader social, behavioral, or cognitive phenomena.

Structuralism as a term, however, was not used by Saussure, who called the approach semiology. The term structuralism is derived from sociologist Émile Durkheim's anti-Darwinian modification of Herbert Spencer's organic analogy which draws a parallel between social structures and the organs of an organism which have different functions or purposes. Similar analogies and metaphors were used in the historical-comparative linguistics that Saussure was part of. Saussure himself made a modification of August Schleicher's language–species analogy, based on William Dwight Whitney's critical writings, to turn focus to the internal elements of the language organism, or system. Nonetheless, structural linguistics became mainly associated with Saussure's notion of language as a dual interactive system of symbols and concepts. The term structuralism was adopted to linguistics after Saussure's death by the Prague school linguists Roman Jakobson and Nikolai Trubetzkoy; while the term structural linguistics was coined by Louis Hjelmslev.

Structural linguistics begins with the posthumous publication of Ferdinand de Saussure's Course in General Linguistics in 1916, which his students compiled from his lectures. The book proved to be highly influential, providing the foundation for both modern linguistics and semiotics. Structuralist linguistics is often thought of as giving rise to independent European and American traditions due to ambiguity in the term. It is most commonly thought that structural linguistics stems from Saussure's writings; but these were rejected by an American school of linguistics based on Wilhelm Wundt's structural psychology.

John E. Joseph identifies several defining features of structuralism that emerged in the decade and a half following World War I:

In Europe, Saussure influenced: (1) the Geneva School of Albert Sechehaye and Charles Bally, (2) the Prague linguistic circle, (3) the Copenhagen School of Louis Hjelmslev, (4) the Paris School of André Martinet and Algirdas Julien Greimas, and the Dutch school of Simon Dik. Structural linguistics also had an influence on other disciplines of humanities bringing about the movement known as structuralism.

Some confusion is caused by the fact that an American school of linguistics of 1910s through 1950s, which was based on structural psychology, (especially Wilhelm Wundt's Völkerpsychologie); and later on behavioural psychology, is sometimes nicknamed 'American structuralism'. This framework was not structuralist in the Saussurean sense that it did not consider language as arising from the interaction of meaning and expression. Instead, it was thought that the civilised human mind is organised into binary branching structures. Advocates of this type of structuralism are identified from their use of 'philosophical grammar' with its convention of placing the object, but not the subject, into the verb phrase; whereby the structure is disconnected from semantics in sharp contrast to Saussurean structuralism. This American school is alternatively called distributionalism, 'American descriptivism', or the 'Bloomfieldian' school – or 'post-Bloomfieldian', following the death of its leader Leonard Bloomfield in 1949. Nevertheless, Wundt's ideas had already been imported from Germany to American humanities by Franz Boas before him, influencing linguists such as Edward Sapir.

Bloomfield named his psychological approach descriptive or philosophical–descriptive; as opposed to the historical–comparative study of languages. Structural linguists like Hjelmslev considered his work fragmentary because it eluded a full account of language. The concept of autonomy is also different: while structural linguists consider semiology (the bilateral sign system) separate from physiology, American descriptivists argued for the autonomy of syntax from semantics. All in all, there were unsolvable incompatibilities between the psychological and positivistic orientation of the Bloomfieldian school, and the semiotic orientation of the structuralists proper. In the generative or Chomskyan concept, a purported rejection of 'structuralism' usually refers to Noam Chomsky's opposition to the behaviourism of Bloomfield's 1933 textbook Language; though, coincidentally, he is also opposed to structuralism proper.

The foundation of structural linguistics is a sign, which in turn has two components: a "signified" is an idea or concept, while the "signifier" is a means of expressing the signified. The "sign", e.g. a word, is thus the combined association of signifier and signified. The value of a sign can be defined only by being placed in contrast with other signs. This forms the basis of what later became the paradigmatic dimension of semiotic organization (i.e., terms and inventories of terms that stand in opposition to each other). This is contrasted drastically with the idea that linguistic structures can be examined in isolation from meaning, or that the organisation of the conceptual system can exist without a corresponding organisation of the signifying system.