Religion was part of everyday life for the Sioux. They believed everything had a spirit.
There were underwater spirits who controlled all animals and plants. High in the sky, they believed there were spirits called Thunderbirds. The Thunderbirds were the most powerful spirits except for the Great Spirit who was the most powerful of all. The Great Spirit was the Sioux God.
Another spirit, The White Buffalo Woman, gave each tribe a sacred pipe. They called these pipes Medicine Pipes. When lit, smokers might be able to have a vision. Visions were powerful things. They believed that dreams and visions were ways to talk to the spirits.
They held religious ceremonies all year long. There was usually only one medicine man per tribe. The medicine man performed ceremonies. Each ceremony usually honored one spirit at a time.