Allopathic medicine, or allopathy, is an archaic and derogatory label originally used by 19th-century homeopaths to describe heroic medicine, the precursor of modern evidence-based medicine . There are regional variations in usage of the term. In the United States, the term is sometimes used to contrast with osteopathic medicine, especially in the field of medical education. In India, the term is used to distinguish conventional modern medicine from Ayurveda, homeopathy, Unani and other alternative and traditional medicine traditions, especially when comparing treatments and drugs.

The terms were coined in 1810 by the creator of homeopathy, Samuel Hahnemann. Heroic medicine was the conventional European medicine of the time and did not rely on evidence of effectiveness. It was based on the belief that disease is caused by an imbalance of the four "humours" (blood, phlegm, yellow bile, and black bile) and sought to treat disease symptoms by correcting that imbalance, using "harsh and abusive" methods to induce symptoms seen as opposite to those of diseases rather than treating their underlying causes: disease was caused by an excess of one humour and thus would be treated with its "opposite".

A study released by the World Health Organization (WHO) in 2001 defined allopathic medicine as "the broad category of medical practice that is sometimes called Western medicine, biomedicine, evidence-based medicine, or modern medicine." The WHO used the term in a global study in order to differentiate Western medicine from traditional and alternative medicine, noting that in certain areas of the world "the legal standing of practitioners is equivalent to that of allopathic medicine" where practitioners can be separately certified in complementary/alternative medicine and Western medicine.

The term allopathy was also used to describe anything that was not homeopathy. Kimball Atwood, an American medical researcher and alternative medicine critic, said the meaning implied by the label of allopathy has never been accepted by conventional medicine and is still considered pejorative. American health advocate and sceptic William T. Jarvis, stated that "although many modern therapies can be construed to conform to an allopathic rationale (e.g., using a laxative to relieve constipation), standard medicine has never paid allegiance to an allopathic principle" and that the label "allopath" was "considered highly derisive by regular medicine." Most modern science-based medical treatments (antibiotics, vaccines, and chemotherapeutics, for example) do not fit Hahnemann's definition of allopathy, as they seek to prevent illness or to alleviate an illness by eliminating its cause.