A trade fair (trade show, trade exhibition, or expo) is an exhibition organized so that companies in a specific industry can showcase and demonstrate their latest products and services, meet with industry partners and customers, study activities of rivals, and examine recent market trends and opportunities.

In contrast to consumer fairs, only some trade fairs are open to the public, while others can only be attended by company representatives (members of the trade, e.g. professionals) and members of the press, therefore trade shows are classified as either "public" or "trade only". A few fairs are hybrids of the two; one example is the Frankfurt Book Fair, which is trade only for its first three days and open to the general public on its final two days.

They are held on a continuing basis in virtually all markets and normally attract companies from around the globe. For example, in the U.S., there are currently over 10,000 trade shows held every year, and several online directories have been established to help organizers, attendees, and marketers identify appropriate events.

Modern trade fairs follow in the tradition of trade fairs established in late medieval Europe, in the era of merchant capitalism. In this era, produce and craft producers visited towns for trading fairs, to sell and showcase products. From the late eighteenth century, industrial exhibitions in Europe and North America became more common reflecting the technological dynamism of the Industrial Revolution.

In the late 19th century, the concept of annual industry-wide trade shows gained traction, spreading from European manufacturing centers to North America. By the 20th century, specialized companies came into existence simply to manage the trade-show industry, and permanent trade show grounds or convention centers were established as venues that featured a rotating calendar of trade shows.

In the 21st century, with the rapid industrialization of Asia, trade shows and exhibitions are now commonplace throughout the Asian continent, with China dominating the exhibitions industry in Asia, accounting for more than 55 per cent of all space sold in the region in 2011.