Nursery web spiders (Pisauridae) is a family of araneomorph spiders first described by Eugène Simon in 1890. They resemble wolf spiders (Lycosidae) except for several key differences. Wolf spiders have two very prominent eyes in addition to the other six, while a nursery web spider's eyes are all about the same size. Additionally, female nursery web spiders carry their egg sacs with their jaws and pedipalps instead of attaching them to their spinnerets as wolf spiders do. When the eggs are about to hatch, a female spider builds a nursery "tent", places her egg sac inside, and stands guard outside, hence the family's common name. Like the wolf spiders, however, the nursery web spiders are roaming hunters that don't use webs for catching prey.

Species occur throughout the world except for extremely dry or cold environments, and are common just about everywhere. Many can walk on the surface of still bodies of water and may even dive beneath the surface temporarily to escape enemies. They can jump a distance of 5 to 6 inches (130 to 150 mm), but they have trouble climbing extremely smooth surfaces such as glass.

The name "nursery web spider" is especially given to the European species Pisaura mirabilis, but this family also includes fishing spiders and raft spiders. Adult female specimens may reach up to 15mm in length, excluding legs. The legs of the male are longer in relation to body size than those of the female.

The female spider sometimes attempts to eat the male after mating. The male, to reduce the risk of this, often presents the female with a gift such as a fly when approaching in the hope that this will satisfy her hunger. Sometimes, this gift is a fake present intended to fool the female. Males may wrap the fake gift in silk, to deceive the female to mate. Females can detect the fake gift and terminate mating, negating the male's deception in not giving a real gift.