The Mandan, self-named Numakiki, are a Native American people who are enrolled in the Three Affiliated Tribes of the Fort Berthold Reservation in North Dakota.

About half of the Mandan reside on the reservation while the rest reside around the United States and in Canada. The Three Affiliated Tribes, also called the MHA Nation, consist of the Mandan, Hidatsa, and Arikara peoples.

They predominantly speak English. However, those on the reservation can also converse in Mandan and Hidatsa. As of 2010, programs in local schools encourage students' learning the language.

They adhere to traditional Mandan beliefs and practices even though Christian missionaries have a long history among them. There are very few evangelical Christians.

"The Mandan's religion and cosmology was highly complex and centered around the figure known as Lone Man. Lone Man was involved in many of the creation myths as well as one of the deluge myths. In their creation myth, the world was created by two rival deities, the First Creator and the Lone Man. The Missouri River divided the two worlds that the beings created. First Creator created the lands to the south of the river with hills, valleys, trees, buffalo, pronghorn antelope and snakes. To the north of the river, Lone Man created the Great Plains, domesticated animals, birds, fish and humans. The first humans lived underground near a large lake. Some of the more adventurous humans climbed a grapevine to the surface and discovered the two worlds. After returning underground, they shared their findings and decided to return with many others. As they were climbing the grapevine, it broke and half the Mandan were left underground." ( Mandan)