海报，中国大陆亦称招贴，通常指单张纸形式、可张贴的广告印刷品。海报是最古老的商业大众传播形式之一，非商业组织及公共机构也有用此宣传方式。其优点是：传播信息及时，能够表达重点，成本费用低，制作简便。

海报可分为公共海报和商业海报两大类：

著名品牌商品的海报时常有成为爱好者的珍藏品，例如经典电影、舞台剧、名星的海报。 另外，海报也可以用作参考历史文献。

A poster is any piece of printed paper designed to be attached to a wall or vertical surface. Typically posters include both textual and graphic elements, although a poster may be either wholly graphical or wholly text. Posters are designed to be both eye-catching and informative. Posters may be used for many purposes. They are a frequent tool of advertisers (particularly of events, musicians and films), propagandists, protestors and other groups trying to communicate a message. Posters are also used for reproductions of artwork, particularly famous works, and are generally low-cost compared to original artwork. The modern poster, as we know it, however, dates back to the 1840s and 1850s when the printing industry perfected colour lithography and made mass production possible."