Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefishes, graylings, taimens and lenoks, which are collectively known as the salmonids ("salmon-like fish"). The Atlantic salmon (Salmo salar), whose Latin name became that of its genus Salmo, is also the source of the family and order names.

Salmonids have a relatively primitive appearance among the teleost fish, with the pelvic fins being placed far back, and an adipose fin towards the rear of the back. They have slender bodies, with rounded scales and forked tails, and their mouths contain a single row of sharp teeth. Although the smallest species is just 13 cm (5.1 in) long as an adult, most are much larger, with the largest reaching 2 m (6 ft 7 in).

All salmonids spawn in fresh water of upper reaches of rivers and creeks, but in many cases, the fish spend most of their adult lives at sea or in brackish estuaries, returning to the rivers only to reproduce. This lifecycle is described as anadromous. Salmonids are carnivorous predators of the middle food chain, feeding on small crustaceans, aquatic insects and smaller fish, and in turn being preyed upon by larger predators. Many species of salmonids are thus considered keystone organisms important for both freshwater and terrestrial ecosystems due to the biomass transfer provided by their mass migration between oceanic and inland waterbodies.