Cornwall is the county that forms the tip of the southwestern peninsula of England; this area has a mild and warm climate regulated by the Gulf Stream. The mild climate allows rich plant cover, such as palm trees in the far south and west of the county and in the Isles of Scilly, due to sub-tropical conditions in the summer.

On Cornwall's moors and high ground areas the high elevation makes tree cover impossible because of the wind, so these areas are populated by shrubs and bushes such as gorse and heather. Ferns, mosses, liverworts, lichens and fungi can all be found in the county. In the wettest areas of Bodmin Moor, sphagnum or bog moss can be found.

Cornwall is home to many rare flower species, especially at the southern end of the Lizard, due to its unique soil and geology. On the Lizard Peninsula, Cornish heath – the floral emblem of Cornwall – mesembryanthemums, butcher's broom, early meadow grass and a wide range of clovers including the Lizard clover, brookweed and yellow wallpepper can be found. The north coast of Cornwall features maritime grassland, heathland and stunted woodland.

In medieval times there were on royal estates and on those of the Bishop of Exeter a number of deer parks in which fallow deer were contained for hunting. The only episcopal manors with deer parks were Lanner, Pawton and Penryn. At Helston in Trigg (Lanteglos) and at Liskeard were probably the oldest deer parks; they were two of the seven which passed from the Earldom to the Duchy of Cornwall in 1337. Among the seven were two at Liskeard (old and new) and a new park at Helston in Trigg and small parks at Launceston and Trematon; the park at Restormel was probably established by Earl Richard. The then existing ducal parks were disparked by King Henry VIII about 1540 so that they became pasture for cattle. There were also a number of privately owned deer parks, both large and small, e.g. Carn Brea, Polrode, Boconnoc and Mount Edgcumbe.

The county's coastal waters are home to large populations of seals. Porpoises, whales and sharks are not uncommonly seen.

Porbeagles inhabit the coastal waters but the etymology of the word is obscure. A common suggestion is that it combines "porpoise" and "beagle", referencing this shark's shape and tenacious hunting habits. Another is that it is derived from the Cornish porth, meaning "harbour", and bugel, meaning "shepherd". The Oxford English Dictionary states that the word was either borrowed from Cornish or formed from a Cornish first element with the English "beagle"; however, none of the proposed Cornish root words are fully satisfactory. Squalus cornubicus (Gmelin, 1789); Squalus cornubiensis (Pennant, 1812) and Lamna cornubica are other Latin names for the porbeagle.

Swanpool is the only location in the British Isles in which the bryozoan Victorella pavida is found.

The sea cliffs host many marine bird species with the red-billed chough recently returning to the county after a long absence. This rare bird appears on the Cornish coat of arms and is the county animal of Cornwall. The nominate subspecies and smallest form, is endemic to the British Isles, where it was restricted to Ireland, the Isle of Man, and the far west of Wales and Scotland, until it recently recolonised Cornwall after an absence of many years.