Sequoia sempervirens (sɛkwɔɪ.ə ˌsɛmpərˈvɪrənz) is the sole living species of the genus Sequoia in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast redwood, giant redwood and California redwood (it is one of three species of trees known as redwoods, but redwood per se normally refers to this species). It is an evergreen, long-lived, monoecious tree living for up to 2,500 — 3,500 years or more, and this species includes the tallest trees on Earth, reaching up to 115.5 m (379.1 ft) in height and 8 m (26 ft) diameter at breast height. It is native to coastal California and the southwestern corner of Oregon within the United States.
The name sequoia is sometimes used as a general term for the subfamily Sequoioideae in which this genus is classified, together with Sequoiadendron (Giant Sequoia) and Metasequoia (Dawn Redwood); as a common name, it usually refers to Sequoiadendron
Coast redwoods have a conical crown, with horizontal to slightly drooping branches. The bark is very thick, up to 30 cm (12 in), and quite soft, fibrous with a bright red-brown when freshly exposed (hence the name redwood), weathering darker. The root system is composed of shallow, wide-spreading lateral roots. The leaves are variable, being 15–25 millimetres (0.59–0.98 in) long and flat on young trees and shaded shoots in the lower crown of old trees, and scale-like, 5–10 millimetres (0.20–0.39 in) long on shoots in full sun in the upper crown of older trees; there is a full range of transition between the two extremes. They are dark green above, and with two blue-white stomatal bands below. Leaf arrangement is spiral, but the larger shade leaves are twisted at the base to lie in a flat plane for maximum light capture. The seed cones are ovoid, 15–32 millimetres (0.59–1.3 in) long, with 15–25 spirally arranged scales; pollination is in late winter with maturation about 8–9 months after. Each cone scale bears 3–7 seeds, each seed 3–4 millimetres (0.12–0.16 in) long and 0.5 millimetres (0.020 in) broad, with two wings 1 millimetre (0.039 in) wide. The seeds are released when the cone scales dry out and open at maturity. The pollen cones are oval, 4–6 millimetres (0.16–0.24 in) long. The species is monoecious, with pollen and seed cones on the same plant.
Its genetic makeup is unusual among conifers, being a hexaploid (6n) and possibly allopolyploid (AAAABB). The mitochondrial genome is (unlike other conifers) paternally inherited..
Coast redwoods occupy a narrow strip of land approximately 750 km (470 miles) in length and 8–75 km (5–47 miles) in width along the Pacific coast of North America; the elevation range is mostly from 30–750 metres (98–2,460 ft), occasionally down to sea level and up to 920 m (about 3,000 feet) (Farjon 2005). They usually grow in the mountains where there is more precipitation from the incoming moisture off the ocean. The tallest and oldest trees are found in deep valleys and gullies, where year-round streams can flow, and fog drip is regular. The trees above the fog layer, above about 700 metres (2,300 ft), are shorter and smaller due to the drier, windier, and colder conditions. In addition, tanoak, pine and Douglas-fir often crowd out redwoods at these elevations. Few redwoods grow close to the ocean, due to intense salt spray, sand and wind. Condensation from coastal fog accounts for a considerable part of the trees' water needs. 
The northern boundary of its range is marked by two groves on the Chetco River on the western fringe of the Klamath Mountains, 25 km (15 miles) north of the California-Oregon border. The largest (and tallest) populations are in Redwood National and State Parks (Del Norte and Humboldt Counties) and Humboldt Redwoods State Park (Humboldt County, California). The southern boundary of its range is the Los Padres National Forest's Silver Peak Wilderness in the Santa Lucia Mountains of the Big Sur area of Monterey County, California. The southernmost grove is in the Southern Redwood Botanical Area, just north of the national forest's Salmon Creek trailhead. 
This native area provides a unique environment with heavy seasonal rains (of up to 2,500 mm or 100 inch annually). Cool coastal air and fog keep this forest consistently damp year round. Several factors, including the heavy rainfall, create a soil with fewer nutrients than the trees need, causing the trees to depend heavily on the entire biotic community of the forest, and complete recycling of the trees when dead. This forest community includes Coast Douglas-fir, Western Hemlock, Tanoak, Pacific Madrone, and other trees along with a wide variety of ferns, Redwood sorrel, mosses and mushrooms. Redwood forests provide habitat for a variety of mammals, birds, reptiles, and amphibians. Old growth redwood stands provide habitat for the federally threatened Spotted Owl and the California-endangered Marbled Murrelet.
The thick, tannin-rich bark, combined with foliage that starts high above the ground provides good protection from both fire and insect damage, contributing to the coast redwood's longevity. The oldest known coast redwood is about 2,200 years old; many others in the wild exceed 600 years. The numerous claims of older trees are incorrect. Because of their seemingly timeless lifespan, coast redwoods were deemed the "everlasting redwood" at the turn of the century; in Latin, "sempervirens" means "ever green" or "everlasting," a coincidence unknown to those who named these giants.
The prehistoric fossil range of the genus is considerably greater, with a subcosmopolitan distribution including Europe and Asia until about 5 million years ago.
Coast redwood reproduces both sexually and asexually. Seed production begins at 10–15 years of age, and large seed crops occur frequently, but viability of the seed is low, typically well below 15%. The low viability may be an adaptation to discourage seed predators, which do not want to waste time sorting chaff (empty seeds) from edible seeds. The winged seeds are small and light, weighing 3.3–5 mg (200-300 seeds/g; 5,600-8,500/ounce). The wings are not effective for wide dispersal, and seeds are dispersed by wind an average of only 60–120 m (200–400 feet) from the parent tree. Growth of seedlings is very fast, with young trees known to reach 20 m (65 feet) tall in 20 years. Coast redwoods can also reproduce asexually by layering or sprouting from the root crown, stump, or even fallen branches; if a tree falls over, it will regenerate a row of new trees along the trunk. This is the reason for many trees naturally growing in a straight line. Sprouts originate from dormant or adventitious buds at or under the surface of the bark. The dormant sprouts are stimulated when the main adult stem gets damaged or starts to die. Many sprouts spontaneously erupt and develop around the circumference of the tree trunk. Within a short period after sprouting, each sprout will develop its own root system, with the dominant sprouts forming a ring of trees around the parent root crown or stump. This ring of trees is called a "fairy ring". Sprouts can achieve heights of 2.3 m (8 feet) in a single growing season.
Redwoods may also reproduce using burls. A burl is a woody lignotuber that commonly appears on a redwood tree below the soil line, though when above, usually within 3 metres (9.8 ft) of the soil. Burls are capable of sprouting into new trees when detached from the parent tree, though exactly how this happens is yet to be studied. Shoot clones commonly sprout from burls and are often turned into decorative hedges when found in suburbia.
The species is very tolerant of flooding and flood deposits, the roots rapidly growing into thick silt deposits after floods.
Coast redwood is one of the most valuable timber species in California, with 899,000 acres (364,000 ha) of redwood forest, all second growth, managed for timber production. Coast redwood lumber is highly valued for its beauty, light weight, and resistance to decay. Its lack of resin makes it resistant to fire.
P. H. Shaughnessy, Chief Engineer of the San Francisco Fire Department wrote:
In the recent great fire of San Francisco, that began April 18th, 1906, we succeeded in finally stopping it in nearly all directions where the unburned buildings were almost entirely of frame construction and if the exterior finish of these buildings had not been of redwood lumber, I am satisfied that the area of the burned district would have been greatly extended.
Because of its impressive resistance to decay, redwood was extensively used for railroad ties and trestles throughout California. Many of the old ties have been recycled for use in gardens as borders, steps, etc. Redwood burls are used in the production of table tops, veneers, and turned goods.
The coast redwood is locally naturalized in New Zealand, notably at Rotorua. Other areas of successful cultivation outside of the native range include Great Britain, Italy, Portugal, the Queen Charlotte Islands, middle elevations of Hawaii, a small area in central Mexico (Jilotepec) and the southeastern United States from eastern Texas to Maryland. Coast redwood trees were used in a display at Rockefeller Center and then given to Longhouse Reserve in East Hampton, Long Island, New York and these have now been living there for over 17 years (2010) and survived 2°F (-17°C).