A trial balloon, also known as kite-flying in the UK and elsewhere, is a term used to describe information sent out to the media in order to observe the reaction of an audience. It is a project or scheme tentatively announced in order to test public opinion. The term comes from the French phrase "ballon dessai," which was a small balloon sent up immediately before a manned ascent to determine the direction and tendency of winds.

Trial balloons are used by companies sending out press releases to judge customer reaction, and by politicians who deliberately leak information on a policy change. In politics, trial balloons often take the form of an intentional news "leak". By releasing information about an idea or proposal to the public, typically through leaking to the media, politicians can gauge the level of support or opposition before making a final decision or taking any action. If public response to the trial balloon is positive, then the politicians in question are likely to follow through with the idea. If public response is negative, then politicians can easily back down from the proposal, since it was never declared officially.