While people in most countries wear wedding rings in the left hand, there are some countries where wearing wedding rings on the right hand is a tradition and custom. Let's take Greek Orthodox people as a typical example. Putting rings on the left hand indicates that they are single and vice versa, wearing rings on the right hand implying that they are married.a
There are many other countries who wear their wedding rings on their right fingers: Norway, Portugal, Spain, some of the countries which made up the former Yugoslavia such as Serbia and Croatia, Russia, the Ukraine, Norway, Bulgaria, Poland Austria, Denmark, Germany, and of course Greece. All of these have very widespread practices, except for Roman Catholics, who do the opposite. In Belgium (at least within the Dutch speaking part) you will wear a it on the left hand, but in the rest of the country, it is typically the right.
In a traditional Jewish ceremony, the groom will place the ring on the bride's index finger, and not the ring finger of either hand at all. Today the ring is often transferred from the index finger to the ring finger after the ceremony (especially in the West), and most Jewish grooms also wear a wedding ring. The reason that Jews use the index finger, is that they believed that it was the most important finger.
Indian brides are also quite confused as to which finger they are to wear the ring on. According to Indian culture, the left hand is less important than the right. But many will wear the ring on the left anyway.