The fretsaw is a bow saw used for intricate cutting work which often incorporates tight curves. Although the coping saw is often used for similar work, the fretsaw is capable of much tighter radii and more delicate work. It has a distinctive appearance due to the depth of its frame (typically between 10 and 20 inches (25 and 51 cm)), which together with the relatively short five-inch (13 cm) blade makes this tool appear somewhat out of proportion compared with most other saws.

Compared with the coping saw it has much shallower blades, which are usually extra-fine, up to 32 teeth per inch (13 teeth per centimetre). This allows much tighter curves to be cut—with many blades even sharp corners are possible—but the blades are also much more fragile compared with that of a coping saw. Unlike the coping saw, the blade has a fixed orientation in relation to the frame. This means that the fretsaw is less useful when cutting long narrow components, but the increased depth of the frame does allow access much further from the edge of the board.

The fretsaw is similar in many respects to the scroll saw, which is essentially a powered fretsaw with a table. Blades between the two tools are usually interchangeable, and indeed scroll saws are often known as "fret saws" informally.

The tool takes its name from its use in fretwork and ultimately from the French freter (lattice)—a reference to the intricate patterns often created using this tool.