Polemic () is contentious rhetoric intended to support a specific position by forthright claims and to undermine the opposing position. The practice of such argumentation is called polemics, which are seen in arguments on controversial topics. A person who writes polemics, or speaks polemically, is called a polemicist. The word derives from Ancient Greek πολεμικός (polemikos) 'warlike, hostile', from πόλεμος (polemos) 'war'.

Polemics often concern questions in religion or politics. A polemical style of writing was common in Ancient Greece, as in the writings of the historian Polybius. Polemic again became common in medieval and early modern times. Since then, famous polemicists have included satirist Jonathan Swift; Italian physicist and mathematician Galileo; French Enlightenment writer, historian, and philosopher Voltaire; Christian anarchist Leo Tolstoy; socialist philosophers Karl Marx and Friedrich Engels; novelist George Orwell; playwright George Bernard Shaw; communist revolutionary Vladimir Lenin; psycholinguist Noam Chomsky; social critics Christopher Hitchens and Peter Hitchens; existential philosopher Søren Kierkegaard; and Friedrich Nietzsche, author of On the Genealogy of Morality: A Polemic.

Polemical journalism was common in continental Europe when libel laws were not as stringent as they are now.

To support study of 17th to 19th century controversies, a British research project has placed online thousands of polemical pamphlets from that period.

Discussions of atheism, humanism, and Christianity have remained open to polemic into the 21st century.