A guerrilla gig is a type of concert performed in a non-traditional setting or arranged in an unusual fashion. It became associated with punk rock, and noise rock bands in UK and the United States during the early to mid-2000s. Bands who perform at such events are sometimes referred to as "guerrilla rockers".

There are two major elements that characterise a guerrilla gig. The first is similar in concept to a flash mob, and involves a band or artist performing in an unexpected, sometimes unannounced, setting not designed to accommodate live music, such as on a bus or subway train, parking lot, or building lobby. The second characteristic involves their being arranged very quickly and without the typical processes of publicity or advance ticket sales. They are usually announced through various internet message boards as well as by text messages and sometimes last-minute flyers.

It is often viewed as an example of punk rock's idealistic "do it yourself" philosophy (which aimed to achieve underground artistic success without commercialisation by avoiding mainstream corporate record labels) being applied via modern communications technology, in a way which would not have been possible before the advent of the internet. The popularity of online forums and social-networking sites has made it possible for bands to immediately disseminate news of a gig to thousands of people only hours before a performance, at minimal cost, and bypassing the traditional print and radio-based methods of publicising concerts.