Meconic acid, also known as acidum meconicum and poppy acid, is a chemical substance found in certain plants of the poppy family, Papaveraceae, such as Papaver somniferum (opium poppy) and Papaver bracteatum.

Meconic acid has erroneously been described as a mild narcotic, but it has little or no physiological activity, and is not used medicinally.

Meconic acid forms salts with alkaloids and metals.

Meconic acid was first isolated by Friedrich Sertürner in 1805.

Meconic acid gives a red color with ferric chloride.