Opodeldoc is a name given by the physician Paracelsus to a sort of liniment which he invented, or at least bestowed this name on. Paracelsus's opodeldoc was a mixture of soap in alcohol, to which camphor and sometimes a number of herbal essences, most notably wormwood, were added. Paracelsus's recipe forms the basis for most later versions of liniment.

Kurt Peters speculates that the curious name opodeldoc was concocted by Paracelsus from syllables from the words "opoponax, bdellium, and aristolochia." Opoponax is a variety of myrrh; bdellium is Commiphora wightii, which produces a similar resin; and aristolochia is a widely distributed genus which includes the snakeroot and many other species. The name suggests that these aromatic plants may have figured in Paracelsus's recipe.

The Pharmacopoeia of the United States (U.S.P.) gives a recipe for opodeldoc that contains:

• Powdered soap, 60 grams;
• Camphor, 45 grams;
• Oil of rosemary, 10 milliliters;
• Alcohol, 700 milliliters;
• Water, enough to make 1000 milliliters

The name Old Opodeldoc was formerly used as a standard name for a stock character who was a physician, especially when played as a comic figure. Edgar Allan Poe used "Opodeldoc" as a pseudonym in a number of places, the best known being the short story The Literary Life of Thingum Bob, Esq. Steer's Opodeldoc was a patent medicine that was widely promoted during Poe's life.