Guide dogs are assistance dogs trained to lead blind and visually impaired people around obstacles. Although the dogs can be trained to navigate various obstacles, they are partially (red-green) color blind and are not capable of interpreting street signs. The human half of the guide dog team does the directing, based upon skills acquired through previous mobility training. The handler might be likened to an aircraft's navigator, who must know how to get from one place to another, and the dog is the pilot, who gets them there safely.

In several countries, guide dogs, along with most service and hearing dogs, are exempt from regulations against the presence of animals in places such as restaurants and public transportation.

References to guide dogs date at least as far back as the mid-16th century; the second line of the popular verse alphabet "A was an Archer" is most commonly "B was a Blind-man/Led by a dog." In the 19th century verse novel Aurora Leigh by Elizabeth Barrett Browning, the title character remarks "The blind man walks wherever the dog pulls / And so I answered."

The first guide dog training schools were established in Germany during World War I, to enhance the mobility of returning veterans who were blinded in combat, but interest in guide dogs outside of Germany didn't become widespread until Dorothy Harrison Eustis, an American dog breeder living in Switzerland, wrote a first-hand account about a guide dog training school in Potsdam, Germany, that was published in The Saturday Evening Post in 1927. Earlier that same year, U.S. Sen. Thomas D. Schall of Minnesota was paired with a guide dog imported from Germany in 1927, but the guide dog movement didn't take hold in America until Nashville resident Morris Frank returned from Switzerland after being trained with one of Eustis's dogs, a female German shepherd named Buddy. Frank and Buddy embarked on a publicity tour to convince Americans of the abilities of guide dogs, and the need to allow people with guide dogs to access public transportation, hotels, and other areas open to the public. In 1929, Eustis and Frank co-founded The Seeing Eye in Nashville, Tennessee (relocated in 1931 to New Jersey).

The first guide dogs in Great Britain were German shepherds. Three of these first were Judy, Meta, and Folly, who were handed over to their new owners, veterans blinded in World War I, on 6 October 1931. Judy's new owner was Musgrave Frankland. In 1934 The Guide Dogs for the Blind Association in Great Britain began operation, although their first permanent trainer was a Russian military officer, Captain Nikolai Liakhoff, who moved to the UK in 1933.