The Pancho Villa Expedition was an abortive punitive expedition conducted by the United States against the military forces of Mexican Revolutionary General Pancho Villa in retaliation for Villa's invasion of the United States and attack on the village of Columbus, New Mexico. The United States Army Center for Military History officially refers to the campaign as the Mexican Expedition. The official beginning and ending dates are March 14, 1916 and February 7, 1917.

Trouble with Villa had been growing since 1915, when the United States government disappointed Villa by giving its support to the Carranza government of Mexico. In revenge, Villa directed his men to harass and harm U.S. citizens along the border. The most serious incident occurred in January 1916, when several American engineers were removed from a train inside Mexico and summarily stripped, executed, and mutilated. Villa kept his men south of the border to avoid a direct confrontation with the U.S. army forces that were being deployed.

On March 9, 1916, Villa's forces attacked Columbus and its small military contingent. They killed several citizens, burned the town, and took many horses and mules, along with a small amount of cash and merchandise removed from shops, before they slipped back into Mexico.

On March 19, on orders from President Woodrow Wilson, General John J. Pershing led an invasion force of 12,000 men into Mexico to capture Villa. The newly adopted airplane, Curtiss JN-2, was used to conduct aerial surveillance. Villa had already had more than a week to disperse and conceal his forces before the punitive expedition tried to seek them out in unmapped, foreign terrain.

Pershing divided his force into two columns to seek out Villa. In June, Lt. George S. Patton raided a small community and killed Julio Cárdenas and two other men. Cárdenas was an important leader in the Villista military organization. In July, U.S. forces mistakenly attacked loyal Mexican troops in the village of Carrizal, killing and wounding many of them.

The expedition bogged down due to its lack of success, tension with Mexican officials and citizens, and the attraction of liquor that was provided by cantinas that remained open all night to provide service to the thirsty soldiers. Another salient feature of the campaign was the regulated brothel operated under official auspices as the "Remount Station", with the rate per copulation set at $2. A prophylactic was issued to each man upon his admission to the precincts, to prevent sexually transmitted infection among the troops.

While the expedition did make contact with Villista formations and killed two of his generals, it failed in its major objectives, stopping neither border raids (which continued while the expedition was in Mexico) nor capturing Villa.

The bulk of American forces were withdrawn in January 1917. Pershing publicly claimed the expedition was a success, although privately he complained to family that President Wilson had imposed too many restrictions, which made it impossible for him to fulfill his mission.

Soldiers who took part in the campaign were honored with the Mexican Service Medal.