Wicca (English: /ˈwɪkə/), is a modern pagan, syncretic, Earth-centred religion. Considered a new religious movement by scholars of religion, the path evolved from Western esotericism, developed in England during the first half of the 20th century, and was introduced to the public in 1954 by Gerald Gardner, a retired British civil servant. Wicca draws upon ancient pagan and 20th-century Hermetic motifs for theological and ritual purposes. Doreen Valiente joined Gardner in the 1950s, further building Wicca's liturgical tradition of beliefs, principles, and practices, disseminated through published books as well as secret written and oral teachings passed along to initiates.

Many variations of the religion have grown and evolved over time, associated with a number of diverse lineages, sects, and denominations, referred to as traditions, each with its own organisational structure and level of centralisation. Given its broadly decentralised nature, disagreements arise over the boundaries that define Wicca. Some traditions, collectively referred to as British Traditional Wicca (BTW), strictly follow the initiatory lineage of Gardner and consider Wicca specific to similar traditions, excluding newer, eclectic traditions. Other traditions, as well as scholars of religion, apply Wicca as a broad term for a religion with denominations that differ on some key points but share core beliefs and practices.

Wicca is typically duotheistic, venerating both a goddess and a god, traditionally conceived as the Triple Goddess and the Horned God, respectively. These deities may be regarded in a henotheistic way, as having many different divine aspects which can be identified with various pagan deities from different historical pantheons. For this reason, they are sometimes referred to as the "Great Goddess" and the "Great Horned God", with the honorific "great" connoting a personification containing many other deities within their own nature. Some Wiccans refer to the goddess as "Lady" and the god as "Lord" to invoke their divinity. These two deities are sometimes viewed as facets of a universal pantheistic divinity, regarded as an impersonal force rather than a personal deity. Other traditions of Wicca embrace polytheism, pantheism, monism, and Goddess monotheism.

Wiccan celebrations encompass both the cycles of the Moon, known as Esbats and commonly associated with the Triple Goddess, alongside the cycles of the Sun, seasonally based festivals known as Sabbats and commonly associated with the Horned God. The Wiccan Rede is a popular expression of Wiccan morality, often with respect to the ritual practice of magic.

Scholars of religious studies classify Wicca as a new religious movement, and more specifically as a form of modern paganism. Wicca has been cited as the largest, best known, most influential, and most academically studied form of modern paganism. It is an eclectic religion, as opposed to reconstructionist paganism.

Several academics also categorise Wicca as a nature religion, a term embraced by many Wiccans, and as a mystery religion. But because Wicca also incorporates the practice of magic, several scholars have referred to it as a "magico-religion". Wicca is also a form of Western esotericism, and more specifically a part of the esoteric current known as occultism. Academics like Wouter Hanegraaff and Tanya Luhrmann have categorised Wicca as part of the New Age, although other academics, and many Wiccans themselves, dispute this.

Although recognised as a religion by academics, some evangelical Christians have attempted to deny it legal recognition as such, while some Wiccans themselves eschew the term "religion", associating it purely with organised religion, and instead favour "spirituality" or "way of life". Wicca is distinct from other forms of contemporary paganism, but there has been "cross-fertilization" between these different faiths. Wicca has both influenced and been influenced by other pagan religions, making clear-cut distinctions more difficult for religious studies scholars. In Wicca, denominations are referred to as traditions, while non-Wiccans are often termed cowans.

When the religion first came to public attention, its followers commonly called it "Witchcraft". Gerald Gardner—the man regarded as the "Father of Wicca"—called it the "Craft of the Wise", "Witchcraft", and "the Witch-cult" during the 1950s. Gardner believed in the theory that persecuted witches had actually been followers of a surviving pagan religion, but this theory has been disproved. There is no evidence that he ever called it "Wicca", although he did call its community of followers "the Wica" (with one c). As a name for the religion, "Wicca" developed in Britain during the 1960s. It is not known who first used this name for the religion, although one possibility is that it was Gardner's rival Charles Cardell, who was calling it the "Craft of the Wiccens" by 1958. The first recorded use of the name "Wicca" was in 1962, and it had been popularised to the extent that several British practitioners founded a newsletter called The Wiccan in 1968.