A plotter is a machine that produces vector graphics drawings. Plotters draw lines on paper using a pen, or in some applications, use a knife to cut a material like vinyl or leather. In the latter case, they are sometimes known as a cutting plotter.

In the past, plotters were used in applications such as computer-aided design, as they were able to produce line drawings much faster and of a higher quality than contemporary conventional printers. Smaller desktop plotters were often used for business graphics. Printers with graphics capabilities took away some of the market by the early 1980s, and the introduction of laser printers in the mid-1980s largely eliminated the use of plotters from most roles.

Plotters retained a niche for producing very large drawings for many years, but have now largely been replaced by wide-format conventional printers. Cutting plotters remain in use in a number of industries.

Digitally controlled plotters evolved from earlier fully analog XY-writers used as output devices for measurement instruments and analog computers.

Pen plotters print by moving a pen or other instrument across the surface of a piece of paper. This means that plotters are vector graphics devices, rather than raster graphics as with other printers. Pen plotters can draw complex line art, including text, but do so slowly because of the mechanical movement of the pens. They are often incapable of efficiently creating a solid region of color, but can hatch an area by drawing a number of close, regular lines.

Plotters offered the fastest way to efficiently produce very large drawings or color high-resolution vector-based artwork when computer memory was very expensive and processor power was very limited, and other types of printers had limited graphic output capabilities.

Pen plotters have essentially become obsolete, and have been replaced by large-format inkjet printers and LED toner-based printers. Such devices may still understand vector languages originally designed for plotter use, because in many uses, they offer a more efficient alternative to raster data.

An X–Y plotter is a plotter that operates in two axes of motion ("X" and "Y") in order to draw continuous vector graphics. The term was used to differentiate it from standard plotters which had control only of the "y" axis, the "x" axis being continuously fed to provide a plot of some variable with time. Plotters differ from inkjet and laser printers in that a plotter draws a continuous line, much like a pen on paper, while inkjet and laser printers use a very fine matrix of dots to form images, such that while a line may appear continuous to the naked eye, it in fact is a discrete set of points.