The House Divided Speech was an address given by senatorial candidate and future president of the United States Abraham Lincoln, on June 16, 1858, at what was then the Illinois State Capitol in Springfield, after he had accepted the Illinois Republican Party's nomination as that state's US senator. The nomination of Lincoln was the final item of business at the convention, which then broke for dinner, meeting again at 8 PM. "The evening session was mainly devoted to speeches", but the only speaker was Lincoln, whose address closed the convention, save for resolutions of thanks to the city of Springfield and others. His address was immediately published in full by newspapers, as a pamphlet, and in the published proceedings of the convention. It was the launching point of his unsuccessful campaign for the senatorial seat held by Stephen A. Douglas; the campaign would climax with the Lincoln–Douglas debates. When Lincoln collected and published his debates with Douglas as part of his 1860 presidential campaign, he prefixed them with relevant prior speeches. The "House Divided" speech opens the volume.

Lincoln's remarks in Springfield depict the danger of slavery-based disunion, and it rallied Republicans across the North. Along with the Gettysburg Address and his second inaugural address, the speech became one of the best-known of his career. It begins with the following words, which became the best-known passage of the speech:

"A house divided against itself, cannot stand."

I believe this government cannot endure permanently half slave and half free.

I do not expect the Union to be dissolved — I do not expect the house to fall — but I do expect it will cease to be divided.

It will become all one thing or all the other.

Either the opponents of slavery will arrest the further spread of it, and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction; or its advocates will push it forward, till it shall become lawful in all the States, old as well as new — North as well as South.^: 9

Lincoln's goals were to differentiate himself from Douglas — the incumbent — and to voice a prophecy publicly. Douglas had long advocated popular sovereignty, under which the settlers in each new territory would decide their own status as a slave or free state; he had repeatedly asserted that the proper application of popular sovereignty would prevent slavery-induced conflict and would allow Northern and Southern states to resume their peaceful coexistence. Lincoln, however, responded that the Dred Scott ruling had closed the door on Douglas's preferred option, leaving the Union with only two remaining outcomes: the country would inevitably become either all slave or all free. Now that the North and the South had come to hold distinct opinions in the question of slavery, and now the issue had come to permeate every other political question, the Union would soon no longer be able to function.