Who is the great I am?
In Exodus of the Old Testament, when God told Moses to go to the king of Egypt and rescue the children of Isreal from their slave bondage. Moses was a bit intimidated and didn’t think he had the capabilities to do such a thing. So he asked God, who should I say is sending me? And God spoke the ultimate words of I Am that I Am (Exodus 3:14) is sending you. (There is not a bigger authority than God Himself.)
When Jesus walked the earth, the Bible tells us that He was God made into a human, but still sinless and holy.
The end of the song, Mary Did You Know? we hear that the newborn Mary cradled was the Great I Am.