Benjamin Louis Eulalie de Bonneville (French pronunciation: [bɛ̃ʒamɛ̃ lwi ølali də bɔnvil]; April 14, 1796 – June 12, 1878) was an American officer in the United States Army, fur trapper, and explorer in the American West. He is noted for his expeditions to the Oregon Country and the Great Basin, and in particular for blazing portions of the Oregon Trail.

During his lifetime, Bonneville was made famous by an account of his explorations in the West written by Washington Irving.

Benjamin was born in or near Paris, France, the son of the French publisher Nicholas Bonneville and his wife Marguerite Brazier. When he was seven, his family moved to the United States; their passage was paid by Thomas Paine. Paine had lodged with the Bonnevilles in France and was godfather to Benjamin and his two brothers, Louis and Thomas. In his will, Paine left the bulk of his estate to Marguerite who had cared for him until he died in 1809. The inheritance included 100 acres (40.5 ha) of his New Rochelle, New York farm where they had been living, so she could maintain and educate her sons.

In 1813 Bonneville received an appointment to the United States Military Academy at West Point, New York. He graduated after only two years, receiving a commission as brevet second lieutenant of light artillery. In his early career, he served at posts in New England, Mississippi, and at Fort Smith in the Arkansas Territory.

In 1824, he was taken to Fort Gibson in the Indian Territory and promoted to captain. While traveling to France, he was a guest of General Lafayette. After returning from France, he was transferred in 1828 to Jefferson Barracks in Missouri.

While in Missouri, Bonneville was inspired by the writing of Hall J. Kelley, as well as editorials in the St. Louis Enquirer (edited at the time by Thomas Hart Benton) to join in the exploration of the American West. Bonneville met with Kelley, who was impressed by him and appointed him to lead one of the expeditions to the Oregon Country; it was scheduled to leave in early 1832. The lack of volunteers for the expedition forced the delay and eventual cancellation of the expedition, leaving Bonneville unrequited in his ambitions.

To pursue his desire to explore the west, he petitioned General Alexander Macomb for a leave of absence from the military, arguing that he would be able to perform valuable reconnaissance among the Native Americans in the Oregon Country, which at the time was under a precarious joint occupation of the U.S. and Britain. It was largely controlled by the Hudson's Bay Company. Macomb granted his request, a 26-month leave running from August 1831 to October 1833, and instructed him to gather all information that might be useful to the government. In particular, he was to pose as a fur trader and find out the natural history of the region, its climates, soils, geography, topography, mineral production, geology, and the character of the local tribes. Expenses for his exploration were paid by private donors, including Astorian Alfred Seton and possibly John Jacob Astor.

Bonneville married and had a daughter with his wife. After both his first wife and daughter died, he did not remarry until after retiring from the military in 1866, when he settled in Fort Smith, Arkansas. There he married Sue Neis.