A travel agency is a private retailer or public service that provides travel and tourism-related services to the general public on behalf of accommodation or travel suppliers to offer different kinds of travel packages for each destination.

Travel agencies can provide outdoor recreation, arranging logistics for luggage and medical items delivery for travellers upon request, public transport timetables, car rentals, and bureau de change services. Travel agencies can also serve as general sales agents for airlines that do not have offices in a specific region. A travel agency's main function is to act as an agent, selling travel products and services on behalf of a supplier. They are also called Travel Advisors. They do not keep inventory in hand unless they have pre-booked hotel rooms or cabins on a cruise ship for a group travel event, such as a wedding, honeymoon, or other group event.

Travel agencies often receive commissions and other benefits and incentives from providers or may charge a fee to the end users. Hotel owners and tour operators typically pay a higher commission rate to travel agencies, whereas airlines typically pay no commission. The customer is normally not made aware of how much the travel agent is earning in commissions and other benefits. A 2016 survey of 1,193 travel agents in the United States found that on average 78% of their revenue was from commissions and 22% was generated from fees.

Travel agencies are recognized by vendors through their accreditation numbers. In the United States, the main accreditation numbers are issued by Airline Reporting Corporation, Cruise Lines International Association, International Air Transport Association.

If more than one travel agency is booking under the same accreditation number, the agency of record is called a host agency. This is a popular model in the United States, with surveys show anywhere from 43-85% of leisure agencies now booking under a host agency.

Travel agencies use the services of the major computer reservations systems, also known as global distribution systems (GDS), including: Amadeus CRS, Galileo GDS, Sabre, and Worldspan, which is a subsidiary of Travelport, which allow for comparison and sorting of hotel and flight rates with multiple companies. Bookings made via travel agents, including online travel agents, may or may not be confirmed instantly. Unlike online travel agencies, metasearch engines and scraper sites, such as Skyscanner, Kayak.com, Rome2rio, and TripAdvisor, travel agencies may or may not have their own booking engine, and instead provide results for search queries and then divert traffic to service providers or online travel agencies for booking. Travel agents may also work with airline consolidators.

Some companies use technology to promote sustainable tourism and bring carbon-neutrality.

A traditional travel agent may work for a travel agency or work freelance. Many traditional agents prefer the term "travel advisor" as opposed to "travel agent" to emphasize their advice, expertise, and connections that are of great value. While most point-to-point travel is now booked online, traditional agents specialize in niche markets such as corporate travel, luxury travel, cruises, complicated and important trips, and specialty trips. Other niche markets for traditional travel agencies include travelers with disabilities, travelers over the age of 60, women traveling alone, LGBT tourism, or a particular group interested in a similar activity, such as a sport.