Temperate rainforests are rainforests with coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain.

Temperate rainforests occur in oceanic moist regions around the world: the Pacific temperate rainforests of North American Pacific Northwest as well as the Appalachian temperate rainforest in the Appalachian region of the United States; the Valdivian temperate rainforests of southwestern South America; the rainforests of New Zealand and southeastern Australia; northwest Europe (small pockets in Great Britain and larger areas in Ireland, southern Norway, northern Iberia and Brittany); southern Japan; the Black Sea–Caspian Sea region from the southeasternmost coastal zone of the Bulgarian coast, through Turkey, to Georgia, and northern Iran.

The moist conditions of temperate rainforests generally have an understory of mosses, ferns and some shrubs and berries. Temperate rainforests can be temperate coniferous forests or temperate broadleaf and mixed forests.

For temperate rainforests of North America, Alaback's definition is widely recognized:

However, required annual precipitation depends on factors such as distribution of rain over the year, temperatures over the year and fog presence, and definitions in other regions of the world differ considerably. For example, Australian definitions are ecological-structural rather than climatic:

Australian definitions would exclude some temperate rainforests of western North America that are Coast Douglas-fir dominant, such as parts of the Klamath Mountains in southern Oregon and northern California, the Puget Lowlands of western Washington and the Georgia Depression in British Columbia, as their dominant tree species, the Coast Douglas-fir, requires stand-destroying disturbance to initiate a new cohort of seedlings. The North American definition would in turn exclude a part of temperate rainforests under definitions used elsewhere.

For forests, canopy refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms (epiphytes, lianas, arboreal animals, etc.). The canopy level is the third level of the temperate rainforest. The trees forming the canopy, conifers, can stand as tall as 100 metres or more. A variety of species survive in the canopy. The tops of these trees collect most of the rain, moisture, and photosynthesis that the rainforest takes in. They form a canopy over the forest, covering about 95% of the floor during the summer.

The canopy's coverage affects the shade tolerance levels of forest floor plants. When the canopy is in full bloom, covering about 95% of the floor, plant survival decreases. Some plant species have become shade tolerant in order to survive. The treetops take in the heavy amount of rain and keep the lower levels of the forest damp.