The fictional universe of the Harry Potter series of novels contains two distinct societies: the "wizarding world" and the "Muggle world". The term "Muggle world" refers to a society inhabited by non-magical humans ("Muggles"), while the term "wizarding world" refers to a society of wizards that live parallel to Muggles. The wizarding world is described as a veiled society wherein magic is commonly used and practised; the wizards live in self-enforced seclusion and hide their abilities from Muggles. The novels are set in 1990s Britain, which contains both Muggle and wizard communities. Any new works taking place in this universe are released under the Wizarding World brand.

The plot of the Harry Potter series occurs between 1991 and 1998. The exceptions are the opening chapter of the first novel, which takes place in 1981, and the epilogue of the seventh novel, which takes place in 2017. The time period setting is primarily derived from the detail in the second novel that the ghost character Nearly headless Nick is celebrating the 500th anniversary of his death date in 1492. At various points throughout the Harry Potter timeline, flashbacks and flash-forwards depict time periods ranging from the 1920s to the 2020s. The depiction of the wizarding world is centred on magic, which not only imbues objects such as wands, but is also portrayed as an inborn ability of individuals. This organic ability can be honed and mastered through study and practice.

Wizards expend a great deal of effort keeping muggles unaware of magic and the wizarding world. The novels explain that in the past, the two worlds co-existed. Over the centuries, persecution of wizards by muggles resulted in the creation of laws designed to keep the wizarding world hidden, such as the International Statute of Wizarding Secrecy of 1692. Enchantment of muggle artifacts is forbidden, underage wizards are restricted from using magic outside of school, and any deliberate revelation of magical ability to the muggle community is punishable. These laws are enforced by the British Ministry of Magic and the International Confederation of Wizards. There are some exceptions: muggle relatives of British wizards are allowed to know about the wizarding world, as is the Prime Minister of the United Kingdom.

The film Fantastic Beasts and Where to Find Them (2016) depicts wizarding laws in the United States during the 1920s. These laws differ in some ways from those in 1990s Britain. For example, the film reveals that American wizards are forbidden from having any social relationships with no-majs / muggles, a condemnatory comparison to the 20th-century American Jim Crow laws and the apartheid system of South Africa.

In the Harry Potter series, some aspects of the wizarding world are depicted as being less-than-modern compared to the muggle world, largely due to the complete incompatibility of magic with electricity. Candles are used for illumination instead of electrical or gas lamps, and owls are used to send messages instead of phone calls or emails. Instead of using pens or computers to take notes and write essays, Hogwarts students use ink-dipped quills and parchment. Wizards do not use paper currency, but instead rely on three types of coins: the gold galleon, equal to 17 silver sickles, which in turn are each equal to 29 bronze knuts — parodying the old pre-decimal British L/S/D coinage system. The wizarding world does have at least one dedicated magical train service, the Hogwarts Express, which is pulled by a steam locomotive. Otherwise, magical carriages are typically camouflaged as goods wagons, cargo vans, and baggage cars on muggle train services, as shown in The Secrets of Dumbledore. The novels depict wizards using a magic-powered equivalent to radio, but there is not an equivalent to television.

The wizarding world of the Harry Potter universe is embedded within the Muggle world. Wizards often live in magical enclaves within muggle villages, such as Godric's Hollow in the West Country. Many wizarding homes in Harry Potter are depicted as being on the outskirts of a muggle town. Only one settlement in Britain, the village of Hogsmeade, is home to an entirely magical population.

The wizarding high street of central London, Diagon Alley, lies just off Charing Cross Road. The Hogwarts Express train departs from King's Cross station using the fictional Platform 9¾. Magical locations are hidden by a combination of muggle-repelling charms, illusions, and other protections. Some magical locations, such as the prison Azkaban and the stadium used for the Quidditch World Cup, are rendered "unplottable", meaning they are impossible to locate on a map. The castle of Hogwarts appears as abandoned ruins to any muggle close enough to see.

Some extremist wizards oppose wizard-muggle marriages, arguing that it dilutes the "purity" of wizard blood. These extremists use the term pure-blood to refer to a wizard who claims to have very little or no muggle blood in their ancestry. Pure-blood supremacists view half-bloods as inferior to them, but superior to muggle-born wizard-folk with muggles at the bottom. These supremacists believe that blood purity is a measure of a wizard's magical ability, although Ron Weasley rebuts this idea by pointing to the existence of so-called pure-blood wizards with low magical skills and claims that "most wizards these days are half-blood". Some families inbreed to maintain blood purity, which can result in offspring with mental instability and violent natures.