The Gadsden flag is a  with a yellow field depicting a  coiled and ready to strike. Beneath the rattlesnake are the words "". Some modern versions of the flag include an apostrophe.

The flag is named for , a  delegate to the  and  in the  who designed the flag in 1775 during the . He gave the flag to Commodore , and it was unfurled on the main mast of Hopkins's   on December 20, 1775. Two days later, Congress made Hopkins  of the . He adopted the Gadsden banner as his personal flag, flying it from the mainmast of the flagship while he was aboard. The  also flew the flag during the early part of the war.

The rattlesnake was a symbol of the unity of the  at the start of the Revolutionary War, and it had a long history as a political symbol in America.  used it for his  woodcut in 1754. Gadsden intended his flag as a warning to  not to violate the liberties of its American subjects.

The flag has been described as the "most popular symbol of the American Revolution." Its design proclaims an  warning of vigilance and willingness to act in defense against coercion. This has led it to be associated with the ideas of  and . It is often used in the United States as a symbol for , , and ; for distrust or defiance against authorities and government.