Thomas Hardwick (1752–1829) was an English architect and a founding member of the Architects' Club in 1791.

Hardwick was born in Brentford, Middlesex the son of a master mason turned architect also named Thomas Hardwick (1725–1798, son of another Thomas, 1681–1746, also a mason, who in 1711 left Herefordshire for Isleworth, where the family retained property, and moved to Brentford in 1725) who worked with the architect brothers Robert and John Adam on nearby Syon House between 1761–1767. Both father and son were associated with Syon from about the 1720s and employment continued until the early 19th century. The Hardwicks were one of the finest architectural families during the 19th century. Thomas Hardwick, his son Philip Hardwick (1792–1870), and then grandson Philip Charles Hardwick (1822–1892) each held the post of Surveyor to St Bartholomew's Hospital, London.

In 1769, aged 17, he enrolled at the new Royal Academy Schools, where he studied architecture under Sir William Chambers, for whom he later worked during the construction of Somerset House. During his first year at the Royal Academy he won the silver medal in architecture, and from 1772 to 1805 he exhibited there.

In his early twenties Hardwick travelled to Europe at his own expense, visiting Paris and Lyon, before heading for Italy accompanied by artist Thomas Jones (1742–1803). He lived in Naples and then Rome for two years from 1776, filling his notebooks with sketches and measured drawings and gaining a grounding in classical architecture which was to influence his own neo-classical style. He also renewed his acquaintance with fellow Academy pupil John Soane (1753–1837).

After returning to London Hardwick established a reputation as a church architect, designing the church of St Mary the Virgin at Wanstead (completed in 1790 – now a Grade I listed building), the Hampstead Road Chapel (1791–1792), St John's Wood Church, St John's Wood High Street (1813–1814), and the church of St Barnabas (now St Clement) King Square, near Old Street. Arguably, his most notable work is the church of St Mary, Marylebone Road (1813–1817).

In 1813 he had begun a chapel-of-ease, designed to accommodate a considerable congregation, on the south side of the New Road in London, for the parish of St Marylebone. It was a basically rectangular building, with two small wings placed diagonally at the liturgical east, and was intended to have an Ionic portico surmounted by a group of figures and a cupola. However, before completion, it was decided that it would make a suitable new parish church for of St Marylebone. Hardwick altered the design to create a suitably grand facade, with a Corinthian portico six columns wide, based on that of the Pantheon in Rome, and a steeple, its top stage in the form of a miniature temple, surrounded by eight caryatids. The interior, with two tiers of galleries supported on iron columns, was left unaltered.

In 1823 he restored St Bartholomew-the-Less in the City of London. An octagonal vaulted interior had been constructed within the church's medieval walls by George Dance the Younger using timber, but had succumbed to dry rot. Hardwick replicated it in more permanent materials, using Bath stone for the columns, and iron for the vaulted ceiling.

He restored Inigo Jones's St Paul's, Covent Garden; he was appointed in 1788 and the eventual 10-year-long restoration project survived an almost disastrous fire in 1795 which destroyed much of Jones's original interior. He also restored Sir Christopher Wren's St James's, Piccadilly.