The United States captures Guam from Spain. The few warning shots fired by the U.S. naval vessels are misinterpreted as salutes by the Spanish garrison, which was unaware that the two nations were at war.

The capture of Guam from Spain by the United States took place in a bloodless engagement during the Spanish–American War. The U.S. Navy sent a single cruiser, USS Charleston, to capture the island of Guam, which was under Spanish control. The Spanish garrison on the island had no knowledge of the war and no real ability to resist the American forces. They surrendered without resistance, and the island passed into American control. The event was the only conflict of the Spanish–American War on Guam.

June 21 is the 172nd day of the year in the Gregorian calendar; 193 days remain until the end of the year.