The right atrioventricular orifice (right atrioventricular opening) is the large oval aperture of communication between the right atrium and ventricle.

Situated at the base of the atrium, it measures about 4 cm. in diameter and is surrounded by a fibrous ring, covered by the lining membrane of the heart; it is considerably larger than the corresponding aperture on the left side, being sufficient to admit the ends of four fingers.