Royal Leamington Spa, commonly known as Leamington Spa or simply Leamington (/ˈlɛmɪŋtən/ ^ⓘ), is a spa town and civil parish in Warwickshire, England. Originally a small village called Leamington Priors, it grew into a spa town in the 18th century following the popularisation of its water which was reputed to have medicinal qualities. In the 19th century, the town experienced one of the most rapid expansions in England. It is named after the River Leam, which flows through the town.

The town contains especially fine examples of Regency architecture, particularly in parts of the Parade, Clarendon Square and Lansdowne Circus. The town also contains several large public parks, such as Jephson Gardens, the Royal Pump Room Gardens and Victoria Park.

Although originally founded around its spa industry, Leamington today has developed into a centre for retail, and digital industries, which has gained it the moniker "silicon spa". In 2023 The Sunday Times named Leamington as the best place to live in the Midlands.

In the 2021 census Leamington had a population of 50,923. Leamington is adjoined with the neighbouring towns of Warwick and Whitnash, and the village of Cubbington; together these form a conurbation known as the "Royal Leamington Spa Built-up area" which in 2011 had a population of 95,172.

Leamington lies around 2.5 miles (4.0 km) east of the county town of Warwick, 9.5 miles (15.3 km) south of Coventry, 22 miles (35 km) southeast of Birmingham, and 81 miles (130 km) northwest of London.

Leamington was originally a small village known as Leamington Priors. Its name came from Anglo-Saxon Leman-tūn or Lemen-tūn = "farm on the River Leam". It was first mentioned in the Domesday Book of 1086 as Lamintone. For 400 years, the settlement was under the control of Kenilworth Priory, from which the older suffix derived. Leamington began to develop as a town at the start of the 19th century, due to the rediscovery of spa waters, which had been known in Roman times, and their rediscovery in 1784 by William Abbotts and Benjamin Satchwell led to their commercialisation, with invalids beginning to resort here in 1786. Six of the seven wells were drilled for; only the original spring at the site of the Aylesford Well, adjacent to the Parish Church, occurred naturally.

The old village of Leamington Priors was on the southern bank of the River Leam, and early development was based around this. During the early 19th century, developers began concentrating the town's expansion on the land north of the river. This resulted in the Georgian centre of New Town with the Leam flowing between the two. By 1810, the town's existing bath houses could not cope with the increasing visitor numbers, and a syndicate was formed to build a new bath house north of the River Leam. A new saline spring was found on land close to the river, belonging to Bertie Greatheed, a wealthy plantation owner and landowner from Guy's Cliffe, and a member of the syndicate. In 1814, the Royal Pump Rooms and Baths were opened on the site, designed by C.S. Smith, who also designed The Regent Hotel and the Upper Assembly Rooms in the town. Spa water can still be sampled outside the building.

Leamington became a popular spa resort attracting the wealthy and famous, with numerous Georgian townhouses to accommodate visitors. Construction of what is now the Parade began in sections from 1808, the Regent Hotel in 1818, a town hall in 1830. and the Jephson Gardens in 1834. In 1838 Queen Victoria granted the town a 'Royal' prefix, and 'Leamington Priors' was renamed 'Royal Leamington Spa'. Queen Victoria had visited the town as a Princess in 1830 and as Queen in 1858. In 1840 the Victoria Bridge was opened, connecting the old and new towns, replacing an old, narrow, and inconvenient bridge. Nine years earlier, the opening of Portobello Bridge, a three-arch bridge over the River Avon, reconnected the town to neighbouring Warwick—an earlier bridge nearby having been condemned and demolished in 1830.