Brodifacoum is a highly lethal 4-hydroxycoumarin vitamin K antagonist anticoagulant poison. In recent years, it has become one of the world's most widely used pesticides. It is typically used as a rodenticide, but is also used to control larger pests such as possums.

4-Hydroxycoumarins are a class of vitamin K antagonist (VKA) anticoagulant drug molecules. Chemically, they are derived from coumarin by adding a hydroxy group at the 4 position to obtain 4-hydroxycoumarin, then adding a large aromatic substituent at the 3-position. The large 3-position substituent is required for anticoagulant activity.