Picea sitchensis, Sitka spruce, is a large coniferous tree in the Pinaceae (pine family) that is the largest of the world's spruces and is one of the most prominent forest trees in stands along the northwest coast of North America. Also known as tideland spruce, coast spruce, and yellow spruce, this coastal species is seldom found far from tidewater, where moist maritime air and summer fogs help to maintain humid conditions necessary for growth. Throughout most of its range from northern California to Alaska, Sitka spruce is associated with western hemlock (Tsuga heterophylla) in dense stands where growth rates are among the highest in North America. It is a valuable commercial timber species for lumber, pulp, and various specialty products, and is the State Tree of Alaska.

Sitka spruce grows in a narrow strip along the north Pacific coast from latitude 61° N. in southcentral Alaska to 39° N. in northern California. The most extensive portion of the range in both width and elevation is in southeast Alaska and northern British Columbia, where the east-west range extends for about 210 km (130 mi) to include a narrow mainland strip and the many islands of the Alexander Archipelago in Alaska and the Queen Charlotte Islands in British Columbia. In Washington, the range includes a narrow mainland strip along the Strait of Georgia, around Puget Sound, up valleys to the east, and on the Olympic Peninsula. On the west side of the Olympic Peninsula, the range broadens to include the extensive coastal plain and seaward mountain slopes. It narrows southward along the Washington and Oregon coast but extends inland for several kilometers along the major rivers. In northern California, the range is more attenuated and becomes discontinuous. A disjunct population in Mendocino County, CA, marks the southern limit of the range.

Sitka spruce usually grows in mixed stands, less often in pure stands. Pure stands usually occur in early successional situations and as tidewater stands influenced by salt spray. Sitka spruce is commonly associated with western hemlock throughout most of its range. Toward the south, other conifer associates include Douglas-fir (Pseudotsuga menziesii), Port-Orford-cedar (Chamaecyparis lawsoniana), western white pine (Pinus monticola), and redwood (Sequoia sempervirens).

Sitka spruce is commercially harvested as pulpwood and for lumbers. High strength-to-weight ratio and resonant qualities of clear lumber are attributes that have traditionally made Sitka spruce wood valuable for specialty uses, such as sounding boards for high-quality pianos; guitar faces; ladders; construction components of experimental light aircraft; oars, planking, masts, and spars for custom-made or traditional boats; and turbine blades for wind energy conversion systems.