Paper wasps are a type of social vespid wasps. The term is typically used to refer to members of the vespid subfamily Polistinae, though it often colloquially includes members of the subfamilies Vespinae (hornets and yellowjackets) and Stenogastrinae, which also make nests out of paper.

Paper wasp nests are characterized by open combs with down pointing cells. Some types of paper wasps are occasionally referred to as umbrella wasps due to the distinctive design of their nests.

Approximately 300 species of Polistes paper wasps have been identified worldwide. The most common paper wasp in Europe is Polistes dominula. The Old World tribe Ropalidiini contains another 300 species, and the Neotropical tribes Epiponini and Mischocyttarini each contain over 250 more, so the total number of true paper wasps worldwide is about 1100 species, almost half of which can be found in the neotropics.

The nests of most true paper wasps are characterized by having open combs with cells for brood rearing. The wasps gather fibers from dead wood and plant stems, which they mix with saliva, and use to construct nests that appear made out of gray or brown papery material that is very similar to handmade paper. A 'petiole', or constricted stalk attaches the nest to a branch or other structure. The wasps secrete an ant repellent chemical which they spread around the base of the petiole or anchor to prevent the loss of eggs or brood.

Most social wasps of the family Vespidae make nests from paper, but some stenogastrine species, such as Liostenogaster flavolineata, use mud. A small group of eusocial crabronid wasps, of the genus Microstigmus (the only eusocial wasps outside the family Vespidae), also constructs nests out of chewed plant fibers, though the nest consistency is quite different from those of true paper wasps, due to the absence of wood fibers, and the use of silk extruded by female wasps to bind the fibers.

Nests can be found in sheltered areas, such as the eaves of a house, the branches of a tree, on the end of an open pipe, or on an old clothesline. Some species, such as Ropalidia romandi, will vary their nest architecture depending on where they build their nest.

Three species of Polistes are obligate social parasites, and have lost the ability to build their own nests, and are sometimes referred to as "cuckoo paper wasps". They rely on the nests of their hosts to raise their brood. A few hornets and yellowjackets are also brood parasites (e.g., Vespula austriaca).

In temperate climates, in the autumn, reproductive males and females are reared. Males find a good place to wait and attract females with pheremones while the queens fly around until they select a mate. Only the new queens hibernate overwinter in a sheltered location; the males and un-mated females die before spring. In the spring each searches for a suitable location and starts and maintains a new nest typically by herself until the first brood of female workers matures and helps in all activities except egg laying.