Because the prayer was taught to the people by Jesus (who is believed by Christians to be God or Lord, as one of the three in The Trinity, the unity of "The Father, Son, and Holy Ghost").
The Lords Prayer as it is known as is not actually a prayer. It was said by Christ as a lesson on how to pray. Man has taken it upon himself to use it as an actual prayer. In Matthew 6:9 we read...
The actual model prayer (Lord's prayer) was given by Jesus at (Matthew 6:9-13) There are two slightly different versions, here is the one used by most English churches (unless they use the Book of...
Personally there is no way to tell if the lords prayer is the "most famous", however it is very popular. As well as the Serenity prayer which goes as follows:
God grand me the serenity to accept the...