Clear and present danger is a term used in the case Schenck v. United States, , a U.S. Supreme Court opinion concerning speech against the draft during World War I (bold emphasis added):

"The question in every case is whether the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent. It is a question of proximity and degree. When a nation is at war, many things that might be said in time of peace are such a hindrance to its effort that their utterance will not be endured so long as men fight, and that no Court could regard them as protected by any constitutional right."

Following Schenck v. United States, "clear and present danger" became a standard test in cases where a United States law limits free speech; the law is deemed to be constitutional if it can be shown that the language it prohibits is language that poses a "clear and present danger."

However, Schenck v. United States, and the "clear and present danger" test, were overturned by Dennis v. United States (1951), which was in turn overturned by Brandenburg v. Ohio (1969), which has replaced the "clear and present danger" test with the "imminent lawless action" test, which continues to be the test of whether speech is constitutionally-protected as of 2004.

Clear and Present Danger is also a book by Tom Clancy, which was made into a movie starring Harrison Ford.