Signal generator, electronic test instrument that delivers an accurately calibrated signal at frequencies from the audio to the microwave ranges. It is valuable in the development and testing of electronic hardware. The signal generator provides a signal that can be adjusted according to frequency, output voltage, impedance, waveform, and modulation.

There are many different types of signal generators with different purposes and applications and at varying levels of expense. These types include function generators, RF and microwave signal generators, pitch generators, arbitrary waveform generators, digital pattern generators and frequency generators. In general, no device is suitable for all possible applications. 

Traditionally, signal generators have been embedded hardware units, but since the age of multimedia PCs, flexible, programmable software tone generators have also been available.