"I Have a Dream" is a public speech that was delivered by American civil rights activist and Baptist minister Martin Luther King Jr. during the March on Washington for Jobs and Freedom on August 28, 1963. In the speech, King called for civil and economic rights and an end to legalized racism in the United States. Delivered to over 250,000 civil rights supporters from the steps of the Lincoln Memorial in Washington, D.C., the speech was one of the most famous moments of the civil rights movement and among the most iconic speeches in American history.

Beginning with a reference to the Emancipation Proclamation, which declared millions of slaves free in 1863, King said: "one hundred years later, the Negro still is not free". Toward the end of the speech, King departed from his prepared text for an improvised peroration on the theme "I have a dream". In the church spirit, Mahalia Jackson lent her support from her seat behind him, shouting, "Tell 'em about the dream, Martin!" just before he began his most famous segment of the speech. Taylor Branch writes that King later said he grasped at the "first run of oratory" that came to him, not knowing if Jackson's words ever reached him. Jon Meacham writes that, "With a single phrase, King joined Jefferson and Lincoln in the ranks of men who've shaped modern America".

The speech was ranked the top American speech of the 20th century in a 1999 poll of scholars of public address. The speech was described by journalist Sean O'Grady in The Independent as having "a strong claim to be the greatest in the English language of all time".

The March on Washington for Jobs and Freedom was partly intended to demonstrate mass support for the civil rights legislation proposed by U.S. president John F. Kennedy in June 1963. Martin Luther King Jr. and other leaders, therefore, agreed to keep their speeches calm to avoid provoking the civil disobedience which had become the hallmark of the civil rights movement. King originally designed his speech as a homage to Abraham Lincoln's 1863 Gettysburg Address, timed to correspond with the centennial of Lincoln's 1863 Emancipation Proclamation.

King had been preaching about dreams since 1960, when he gave a speech to the National Association for the Advancement of Colored People (NAACP) called "The Negro and the American Dream". This speech discusses the gap between the American Dream and reality, saying that overt white supremacists have violated the dream, and that "our federal government has also scarred the dream through its apathy and hypocrisy, its betrayal of the cause of justice". King suggests that "It may well be that the Negro is God's instrument to save the soul of America." In 1961, he spoke of the civil rights movement and student activists' "dream" of equality—"the American Dream ... a dream as yet unfulfilled"—in several national speeches and statements and took "the dream" as the centerpiece for these speeches.

On November 27, 1962, King gave a speech at Booker T. Washington High School in Rocky Mount, North Carolina. That speech was longer than the version which he would eventually deliver from the Lincoln Memorial. And while parts of the text had been moved around, large portions were identical, including the "I have a dream" refrain. After being rediscovered in 2015, the restored and digitized recording of the 1962 speech was presented to the public by the English department of North Carolina State University.

King had also delivered a speech with the "I have a dream" refrain in Detroit, in June 1963, before 25,000 people in Detroit's Cobo Hall immediately after the 125,000-strong Great Walk to Freedom on June 23, 1963. Reuther had given King an office at Solidarity House, the United Auto Workers headquarters in Detroit, where King worked on his "I Have a Dream" speech in anticipation of the March on Washington. Mahalia Jackson, who sang "How I Got Over" at the march just before King's speech, knew about the Detroit speech. After the March on Washington, a recording of King's Cobo Hall speech was released by Detroit's Gordy Records as an LP entitled The Great March To Freedom.

King's speech at the March on Washington was drafted with the assistance of Stanley Levison and Clarence Benjamin Jones in Riverdale, New York City. Jones has said that "the logistical preparations for the march were so burdensome that the speech was not a priority for us" and that, "on the evening of Tuesday, Aug. 27, (12 hours before the march) Martin still didn't know what he was going to say".