This paper presents a comprehensive academic study of Urdu antonymy, a fundamental lexical-semantic opposition that plays a crucial role in the structure and meaning of Urdu. As one of the primary forms of lexical opposition, antonymy serves as an important mechanism for expressing distinctions and conveying a wide range of meanings. After situating antonymy within the theoretical framework of lexical semantics, the paper defines the concept and distinguishes it from related semantic relations such as hyponymy and polysemy. It then examines the significance of antonymy in three interrelated fields: linguistics, particularly semantic theory; language acquisition, where antonymic relations facilitate vocabulary and concept learning; and the philosophy of language, where they contribute to discussions of meaning, opposition, and categorisation. A major portion of the study is devoted to the classification of antonyms in Urdu. It analyses gradable antonyms, which represent opposite ends of a continuum and allow intermediate degrees (e.g., بڑا/چھوٹا, big/small); complementary antonyms, which denote mutually exclusive categories with no middle ground (e.g., مردہ/زندہ, dead/alive); relational antonyms, which express reciprocal relationships (e.g., اُستاد/شاگرد, teacher/student); reversive antonyms, which denote actions or processes that undo one another (e.g., آنا/جانا, come/go); and directional antonyms, which signify opposite orientations or movements (e.g., اوپر/نیچے, upward/downward). For each category, the paper provides theory-based definitions, identifies distinguishing semantic features, presents authentic examples from classical poetry, modern literature, and everyday speech, and examines the syntactic behaviour of antonyms in Urdu sentence structures.