Fly fishing is a distinct and ancient angling method which uses flies that are cast with a special fishing rod and line.

Fly fishing can be done in fresh or salt water. Freshwater fishing is often divided into coldwater (trout, salmon, steelhead), coolwater (pike, perch, walleye), warmwater (bass, chub, catfish) fishing. The techniques for freshwater fly fishing also differ in lakes, streams and rivers.

In fly fishing, fish are caught by using artificial flies that are cast with a fly rod and a fly line. The fly line (today, almost always coated with plastic) is heavy enough in order to send the fly to the target. This is one of the main differences between spinner and bait rods, which use heavy weight on the line to cast lures, bait, etc. Artificial flies can vary dramatically in all morphological characteristics (size, weight, colour, etc.).

Artificial flies are created by tying hair, fur, feathers, or other materials, both natural and synthetic, onto a hook with thread. The first flies were tied with natural materials, but synthetic materials are now very popular and prevalent. The flies are tied in sizes, colours and patterns to match local terrestrial and aquatic insects, baitfish, or other prey attractive to the target fish species.

Fish species
Fly fishing is most renowned as a method for catching trout and salmon, but today it is also used for a wide variety of species including pike, bass, panfish, grayling and carp, as well as marine species, such as redfish, snook, tarpon, bonefish and striped bass. There are many reports of fly anglers taking unintended species such as chub, bream and rudd while fishing for 'main target' species such as trout. There is a growing population of anglers whose aim is to catch as many different species as possible with the fly. Even catfish can be occasionally caught while fly fishing.

Many credit the first recorded use of an artificial fly to the Roman Claudius Aelianus near the end of the 2nd century. He described the practice of Macedonian anglers on the Astraeus River:

...they have planned a snare for the fish, and get the better of them by their fisherman's craft. . . . They fasten red . . . wool round a hook, and fit on to the wool two feathers which grow under a cock's wattles, and which in colour are like wax. Their rod is six feet long, and their line is the same length. Then they throw their snare, and the fish, attracted and maddened by the colour, comes straight at it, thinking from the pretty sight to gain a dainty mouthful; when, however, it opens its jaws, it is caught by the hook, and enjoys a bitter repast, a captive.
In his book Fishing from the Earliest Times, however, William Radcliff (1921) gave the credit to Martial (Marcus Valerius Martialis), born some two hundred years before Aelian, who wrote:

...Who has not seen the scarus rise, decoyed and killed by fraudful flies...
The last word, somewhat indistinct in the original, is either "mosco" (moss) or "musca" (fly) but catching fish with fraudulent moss seems unlikely.