In the localised Celtic polytheism practised in Great Britain, Sulis was a deity worshiped at the thermal spring of Bath. She was worshiped by the Romano-British as Sulis Minerva, whose votive objects and inscribed lead tablets suggest that she was conceived of both as a nourishing, life-giving mother goddess and as an effective agent of curses invoked by her votaries.

The exact meaning of the name Sulis has been a matter of debate, but an emerging consensus among linguists regards the name as cognate with Old Irish súil ("eye, sight").

A common Proto-Celtic root *sūli-, related to the various Indo-European words for "sun" (cf. Homeric Greek ἡέλιος, Sanskrit sūryah, from c *suh₂lio-) has also been proposed, although the Brittonic terms for "sun" (Old Breton houl, Old Welsh heul) feature a diphthong that is absent from Sulis and they are not attested as a feminine form or with the -i- inflection. Pierre-Yves Lambert argues for a Proto-Celtic form *su-wli-, composed of the prefix su- ("good") attached to the Celtic verbal theme *wel- ("to see").

The medieval Welsh personal name Sulgen (< Sulien; "born from Sulis") and the Breton personal name Sul, borne by a local saint, are also related.

Sulis was the local goddess of the thermal springs that still feed the spa baths at Bath, which the Romans called Aquae Sulis ("the waters of Sulis"). Sulis was likely venerated as a healing divinity, whose sacred hot springs could cure physical or spiritual suffering and illness. According to scholar Miranda Green, the cult of Sulis at Bath was active until the mid-fourth century CE. Her name primarily appears on inscriptions discovered in an extensive temple area to her at Bath, with only a single instance outside of Britain at Alzey, Germany.

At the Roman temple at Bath, several ancient additions to the altar area suggest that sacrifice there was a major part of worshipping the goddess. The open area surrounding the altar may have been used for processions and public offerings of meats and liquids. A majority of the finds at the spring consist of coins and curse tablets (see "Inscribed tablets" section next), with over 12,500 Roman coins and 18 Celtic coins having been found in the reservoir. In addition, items have also been retrieved that were likely private offerings, such as jewelry, gemstones, plates, bowls, military items, wooden and leather objects.

Pewter vessels found in the spring reservoir have led some scholars to conclude that physical contact with the water may have been important for transfer of healing properties, with these vessels being used to pour the water over visitors' bodies.

From the evidence of funerary inscriptions discovered on the site, it appears that visitors to the sacred springs may have included retired soldiers, soldiers acting as tourists, and/or soldiers looking for relief from injury or illness. In order to afford the inscriptions, those who recorded their visit with altars or tombstones would likely have been of higher status.