The "Day of Infamy" speech, sometimes referred to as just "The Infamy speech", was delivered by Franklin D. Roosevelt, the 32nd president of the United States, to a joint session of Congress on December 8, 1941. The previous day, the Empire of Japan attacked the United States military bases at the Pearl Harbor, Hawaii, and the Philippines, and declared war on the United States and the British Empire. The speech is known for its first line: "Yesterday, December 7, 1941—a date which will live in infamy..."

On Sunday, December 7, 1941, the American naval base at Pearl Harbor in the Territory of Hawaii was attacked by 353 Imperial Japanese Navy Air Service aircraft in a surprise military strike, destroying various American ships and aircraft, and killing over 2,400 civilians and military personnel. After consulting with his cabinet, Roosevelt decided to deliver an address before the joint session of the Congress the next day.

Roosevelt's speech was worded to reinforce his portrayal of the United States as a victim of unprovoked Japanese aggression and appealed to patriotism rather than to idealism. Roosevelt employed the idea of kairos, which relates to speaking promptly. It made the speech powerful and rhetorically important. According to author Sandra Silberstein, Roosevelt's speech followed a well-established tradition of how "through rhetorical conventions, presidents assume extraordinary powers as the commander in chief, dissent is minimized, enemies are vilified, and lives are lost in the defense of a nation once again united under God."

The speech had an immediate positive response and long-lasting impact. It is one of the most famous speeches of American politics. It was broadcast live by radio and attracted the largest audience in American radio history, with over 81% of people tuning in to hear the speech. Soon after the speech, Congress almost unanimously declared war against Japan, formally entering World War II. The White House later received a number of telegrams praising Roosevelt's stance. The speech has since been used in various films. Roosevelt's description of December 7, 1941, as "a date which will live in infamy" has been compared with November 22, 1963, the assassination of John F. Kennedy, the September 11 terrorist attacks, and January 6, 2021, the storming of the United States Capitol.