寒蝉效应（英语：Chilling Effect）法律用语，是指当下对言论自由的「阻吓作用」——即使是法律没有明确禁止的。然而，在一般情况下，寒蝉效应现在经常以法律或不明确行动施加不必要的负担，来禁止合法的讲话。该词词源自美国法律，早于1950年使用。然而，进一步明确使用，是在美国最高法院法官小威廉·布伦南，用在司法判决中，作为一个法律术语。

在中文里，将「Chilling Effect」翻成寒蝉效应，是源自成语「噤若寒蝉」。《后汉书‧杜密传》云：「刘胜位为大夫，见礼上宾，而知善不荐，闻恶无言，隐情惜己，自同寒蝉，此罪人也。」古人认为「蝉嘶于夏秋，不久即死。」古人不察，以为蝉到寒天，不能发声。乃以噤若寒蝉形容不敢作声。

In a legal context, a chilling effect is the inhibition or discouragement of the legitimate exercise of natural and legal rights by the threat of legal sanction. The right that is most often described as being suppressed by a chilling effect is the US constitutional right to free speech. A chilling effect may be caused by legal actions such as the passing of a law, the decision of a court, or the threat of a lawsuit; any legal action that would cause people to hesitate to exercise a legitimate right (freedom of speech or otherwise) for fear of legal repercussions. When that fear is brought about by the threat of a libel lawsuit, it is called libel chill. A lawsuit initiated specifically for the purpose of creating a chilling effect may be called a Strategic Lawsuit Against Public Participation, or more commonly called; a "SLAPP suit."