The German cockroach or Croton bug (Blattella germanica) is a small species of cockroach, measuring about 1/2" to 5/8" (1.3 cm to 1.6 cm) long. It is tan to light brown, and has two dark parallel streaks running from the head to the base of the wings. Although it has wings, it is not very skilled at flight and is unable to sustain flight.

The German cockroach is one of the most common and prominent household cockroaches in the world, and can be found throughout many human settlements in the world. In colder climates, it is found only near human habitats, since it is not very tolerant towards the cold. The German cockroach is originally from Asia, and is also very closely related to the Asian cockroach, to the extent that to the casual observer they appear nearly identical and may be mistaken for the other.

The German cockroach is very successful at establishing a niche in buildings, and is very hardy and resilient towards attempts to exterminate them. This is due to the fact they produce a large number of nymphs for each egg case, and that there is a short period between birth and sexual maturity. The mother also carries the egg case with her during the germination period, rather than depositing the egg case like other species, a practice which would leave them vulnerable in a human habitat against zealous attempts to wipe them out. Theoretically, a single female could account for up to 91,000 offspring within a three month period. The cockroach is also smaller than many other species so it can more easily hide and fit into very small cracks and crevices to evade humans. The German cockroach, discounting the presence of pets, has few natural predators inside a human habitat.

The German cockroach eats a wide variety of items. They particularly like starch, sugary foods, grease and meats. The cockroach can be seen in the day, especially if there is a large population or if they have been disturbed; sightings are commonly reported in the daytime hours. However, they are nocturnal, and therefore most active at night.