The Battle of Fort Rivière was the decisive battle of the First Caco War during United States occupation of Haiti in 1915. A combined force of U.S. Marines and sailors defeated Cacos rebels at Fort Rivière, ending the First Caco War.

In 1915, United States forces landed in Haiti during a period of political instability. Cacos insurgents, quasi-military mountain tribes who served as mercenaries for the highest bidder, routinely attacked political targets, as well as ordinary Haitians, to sustain themselves. By October, United States Marines had trapped the Cacos in the mountains of northeastern Haiti, and moved in to eradicate them. On 25 October, Marines from the 15th Company, 2nd Marine Regiment, under the command of Major Smedley Butler, had dealt the Cacos a significant blow at the Battle of Fort Dipitié, and shortly thereafter took its parent Fort Capois with heavy Cacos casualties. On 8 November, Butler's force captured Forts Selon and Berthol without resistance, leaving Fort Rivière as the final Cacos stronghold.

Fort Rivière had been built by the French in the latter 1700s out of brick and stone atop Montagne Noire, at an elevation of 4,000 feet (1,200 m). Due to the harsh terrain, the Marine brain trust considered the fort impregnable unless a whole regiment with artillery was sent to attack, but Major Butler convinced Colonel Eli K. Cole that he could take the fort with 100 men. Butler assembled a force from 5th, 13th, and 23rd Marine companies, as well as from the Marines and sailors aboard the USS Connecticut.

At dusk on 16 November, Butler's force began its ascent of the mountain toward the fort. At daybreak on 17 November, Butler deployed the 23rd Company, along with the Marines and bluejackets from the Connecticut, on the fort's south wall. Captain Chandler Campbell led the 13th Company up the east wall and Butler led the 5th Company up the west wall. The attack commenced at 07:30 and the Marines immediately began taking fire—Butler described it as "heavy, but inaccurate"—with scant cover.

Butler's company located a partially sealed drain 4 feet (1.2 m) wide, 3 feet (0.91 m) tall, and 15 feet (4.6 m) deep in the fort's wall, which served as a Cacos entrance. Sergeant Ross Lindsey Iams and Private Samuel Gross were the first through the tunnel, followed by Butler with his .45 caliber pistol. The trio of Marines immediately began to fire on the 75 surprised Cacos in the fort—Butler described them as "half naked madmen, howling and leaping"—and they were joined shortly by the rest of the 5th Company streaming through the drain. Private Gross dispatched a massive Cacos with his rifle just moments before he would have struck a devastating blow to Butler's head with a club. As panic overtook the Cacos, Butler wrote that they "threw away their loaded guns and grabbed swords and clubs, rocks and bricks, which were no match for bullets and bayonets." After ten minutes of intense hand-to-hand combat, the Marines had killed some 50 Cacos and taken the remainder prisoner; those who had escaped the fort were cut down or captured by the force covering the south wall.

The American force had won an "astounding little victory" and had suffered no casualties—one man lost two teeth to a thrown rock—despite a sharp conflict. Butler wrote that if the defenders "had only realized the advantage of their position, they could have shot us like rats as we crawled, one by one, out of the drain." Having delivered a massive blow to the Cacos themselves, the Marines leveled Fort Rivière with dynamite and destroyed 60 dwellings outside the fort, thus ending the First Caco War. Butler wrote that the returning Americans were greeted by Haitians roadside, who were grateful for "ridding them of the Caco terror" that had plagued the countryside. Armed resistance to the American occupation did not end, however, as minor skirmishing continued until the Second Caco War (1918–1920) erupted.

For their heroism during the Battle of Fort Rivière, Major Butler, Sergeant Iams, and Private Gross all received the Medal of Honor; the award was Butler's second, having received the first the prior year during the Battle of Veracruz.

• Banana Wars
• Battle of Fort Dipitié