A spinnerbait or spinner is any one of a family of hybrid fishing lures that combines the designs of a swimbait with one or more spoon lure blades. Spinnerbaits get the name from the action of the metallic blades, which passively revolve around the attachment point like a spinning propeller when the lure is in motion, creating varying degrees of vibration and flashing that mimic small fish or other preys of interest to large predatory fishes. The two most popular types of spinnerbaits are the in-line spinner and safety pin spinnerbait, though others such as the tail spinner also exist. Spinnerbaits are used principally for catching freshwater fishes such as perch, pike and bass.

Spinnerbaits attract predatory fish primarily by creating significant amount of turbulence, noise and flashing reflections with the spinning blade. The turbulence waves, in particular, provoke the fish's lateral line system, a special tactile sensory organ that enables fish to detect vibrations transmitted through the water and "feel" objects at a distance. Most fish have well-developed lateral lines and can detect the slightest disturbance in water around it, which may warn fish of approaching dangers, signal the presence of territorial intruders, or indicate the potential location of prey.

Spinnerbait blades also functions as individual spoon lures, mimic prey and stimulate other fish senses by creating flashes (sight) and noises (hearing) that can be detected quite far away in clear, calm water conditions.

The most important part of any spinnerbait next to the hook is the blade. There are several different shapes, and numerous sizes, with colors ranging from gold, silver, and bronze, to painted blades with a myriad of different colors and patterns. The two main characteristics of a spinnerbait blade are flash (available light reflecting off the blade as it moves) and vibration (the 'thump' of the blade as it spins). Some blade designs produce more vibration, while other designs produce more flash. Each blade applies to different scenarios, making it crucial to properly arm and prepare yourself for multiple weather conditions. The most prominent blade types include the following:

The in-line spinner is named for the fact that a metal blade revolves around a central axis (a wire), which may be attached by a clevis (a c-shaped metal piece with holes that accommodates the wire) or by itself. Most in-line spinners have metal weights rigged behind the spinning blade and beads or brass hardware that separates the two for frictionless spinning. Due to the fact that the spinning blade cause the whole bait to rotate, line twist builds that creates line problems and tangles. Swivels are used to solve the problem of twist.

As with all spinner type baits, various shapes of blades are used depending on many factors. Speed of retrieve is a major consideration because different blade designs revolve at different speeds. For example, the elongated willow leaf design requires the most speed to start and maintain the spin. The broader and more circular Colorado blade requires less speed and a slower retrieve to maintain spin. An Indiana blade falls somewhere in between. Vibration is higher with broader blades, less with streamlined blades, but flash depends more on blade size, texture and color than on design.

A hammered nickel (pock-marked) blade has the most flash in that the dimpling reflects light at more angles than a smooth polished blade. Painted blades can have more or less flash depending on color and patterns, but always less flash than silver finishes under a sunny sky and have more flash under low light conditions. Under low light conditions fluorescent colored blades stand out over regular colors or polished metal.

The treble hook can be dressed or not, depending on personal preferences of bait profile and action. By itself, the flash and maybe the vibration are the only attractors. But anytime you add something to a bait, you change its appearance and action and may have to alter presentation.