Quinidine is a pharmaceutical agent that acts as a class I antiarrhythmic agent in the heart. It is a stereoisomer of quinine, originally derived from the bark of the cinchona tree.

Chemically it is known as (2-ethenyl-4-azabicyclo^*oct-5-yl)- (6-methoxyquinolin-4-yl)-methanol OR

6'-mehoxycinchonan-9-ol