A spider web, spiderweb, spider's web, or cobweb (from the obsolete word coppe, meaning "spider") is a device created by a spider out of proteinaceous spider silk extruded from its spinnerets.

Spider webs have existed for at least 100 million years, as witnessed in a rare find of Early Cretaceous amber from Sussex, southern England. Insects can get trapped in spider webs, providing nutrition to the spider; however, not all spiders build webs to catch prey, and some do not build webs at all. "Spider web" is typically used to refer to a web that is apparently still in use (i.e. clean), whereas "cobweb" refers to abandoned (i.e. dusty) webs. However, "cobweb" is used to describe the tangled three-dimensional web of some spiders of the Therididae family. Whilst this large family is also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, they actually have a huge range of web architectures.