A terrarium is a clear container (often plastic or glass) used to grow plants and to examine or hold small creatures. They may be cubical, spherical, rectangular, or other shapes. Often in terraria the species' ecosystem is copied in smaller size and is even controlled in humidity, temperature, and water chemistry.

Animals commonly held in terraria include reptiles, amphibians, fish, insects, spiders, and scorpions. Many kinds of plants are suitable for a terrarium, including bromelids and orchids, as well as any kind of underwater plant.

There are various forms of terraria, including:

  • aquarium
  • aqua-terrarium
  • desert terrarium
  • insectarium
  • tropical terrarium
  • vivarium
  • paludarium