A single-layer printed circuit board (PCB) is a type of PCB that has components and conductive tracks on only one side of the board. It is typically made of a non-conductive substrate, such as fibreglass or plastic, with a thin layer of metal, usually copper, applied to one side. The metal layer is then etched to create the desired circuit patterns and connections.

Single-layer PCBs are relatively simple and inexpensive to manufacture, making them a popular choice for prototyping and low-volume production. However, they have limited space for components and are not suitable for more complex designs that require a higher density of components. They are also more prone to crosstalk and signal interference due to the close proximity of the components and traces.