蜘蛛网是由部分种类的蜘蛛吐丝所编成的网状物，用以捕获昆虫、小型脊椎动物等作食物，或用以结巢居住。蜘蛛可以感应到猎物冲撞或受困于蜘蛛网上时所产生的震动；在完成牠们的网后，蜘蛛会在网上或附近等待猎物落入陷阱。蜘蛛网里有些丝有黏性，有些没有。由于蜘蛛本身的行动也会受自己的黏液所影响，因此当牠们在网上移动时，会避免踩到带有黏液的丝线。

有一些蜘蛛丝的强度比同等重量的钢丝还要强，弹性也较高。是材料学的研究课题之一，具有产业上的潜在应用价值，可使用于制造防弹背心或人造肌腱等物品。而为了制造人造蜘蛛丝，有些研究者利用基因改造的哺乳动物来生产所需的蛋白质。

A spider web, spiderweb, spider's web, or cobweb (from the archaic 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 theridiidae family. While 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.