The Cooper Union speech or address, known at the time as the Cooper Institute speech, was delivered by Abraham Lincoln on February 27, 1860, at Cooper Union, in New York City. Lincoln was not yet the Republican nominee for the presidency, as the convention was scheduled for May. It is considered one of his most important speeches. Some historians have argued that the speech was responsible for his victory in the presidential election later that year.

In the speech, Lincoln elaborated his views on slavery by affirming that he did not wish it to be expanded into the western territories and claiming that the Founding Fathers would agree with this position. The journalist Robert J. McNamara wrote, "Lincoln's Cooper Union speech was one of his longest, at more than 7,000 words. And it is not one of his speeches with passages that are often quoted. Yet, due to the careful research and Lincoln's forceful argument, it was stunningly effective."