Wedding Rings Were Not Always Worn on the Left Hand

The tradition of wearing a wedding ring on the left hand's fourth finger comes from the Roman belief in the "vena amoris" — the "vein of love" believed to run directly from that finger to the heart. Modern anatomy disproved this, but the tradition persisted. In many European countries, including Germany and Russia, wedding rings are worn on the right hand instead.

Source: The History of Marriage — Edward Westermarck