German aristocratic naturalist, ethnographer, and explorer whose observations on a trip to the American West in the 1830s provide valuable information about the Plains Indians at that time.

Maximilian was the prince of the small state of Neuwied and served in the Prussian army. He undertook explorations in Brazil in 1815–17 and in North America in 1832–34. On the latter journey, he took with him the Swiss artist Karl Bodmer to record the landscapes and peoples they encountered. They traveled from Boston westward along the Ohio River to St. Louis, Mo., from where they traveled by steamboat up the Missouri River through what are now Missouri, Nebraska, South Dakota, North Dakota, and Montana. The westernmost point they reached on their journey was Fort McKenzie, a trading post in central Montana. Maximilian made copious notes of his contacts with the Mandan, Hidatsa, and other Indian tribes of the Missouri River area, while Bodmer made hundreds of superb watercolours and drawings of the landscapes and the Indians they encountered.

Maximilian's notes and Bodmer's pictures form an invaluable account of the language, dress, culture, and customs of several Indian tribes that subsequently almost disappeared owing to disease, war, and white encroachment on their lands. Maximilian wrote up his observations in Reise in das innere Nord-America in den Jahren 1832 bis 1834, 2 vol. (1839–41; Travels in the Interior of North America). An English translation of parts of his field journal was published in People of the First Man: Life Among the Plains Indians in Their Final Days of Glory (1976).