Thomas Hopper (1776–1856) was an English architect of the late 18th and early 19th centuries, much favoured by King George IV, and particularly notable for his work on country houses across southern England, with occasional forays further afield, into Wales and Ireland (especially Ulster).

He was involved with improvements to the Shire Hall in Monmouth under "Royal assent", where he and Edward Haycock made the building extend down Agincourt Street, creating room for a new staircase and larger courts. Hopper took up residence in Monnow Street in Monmouth whilst this was in progress.^[1]

In 1840 he exhibited designs for Butterton Hall in Staffordshire. This gothic building lasted until the First World War when it was demolished due to misuse.^[2]

Hopper died in 1856.^[2]

• Leigh Court, North Somerset (1814)^[3]
• Penrhyn Castle, Llandegai, Bangor, North Wales (1822–1837)^[4]
• Kentwell Hall, Suffolk (1820s)
• Arthur’s Club, 69–70 St James’s Street, London (after 1940 the Carlton) (1826–1827)
• Llanover Hall, Abergavenny, Wales (1827–1837; demolished 1935)
• Improvements to the Shire Hall, Monmouth (1829)^[1]
• Bryn Bras Castle, Llanrug, North Wales (1829–1835)^[5]
• Margam Castle, South Wales (1830–1840)
• Wivenhoe House, Essex (1846–1853)
• Hospital buildings at St Mary's Hospital, Paddington, London (1851)
• Alscot Park, Warwickshire
• Amesbury Abbey, Wiltshire (1834–1840 and 1859–1860): a country house named for the nearby former abbey; Grade I listed^[6]
• Boreham House, Essex
• Gothic Conservatory at Carlton House, London, demolished
• Crichel House, Dorset, alterations
• Danbury Place, Essex
• Easton Lodge, Essex
• Englefield House, Berkshire
• Gosford Castle, County Armagh
• Chapel at Stansted Park, West Sussex
• Glemham House, Great Glenham, Suffolk (1814)^[7]
• Terling Place, Essex (1818–1824): alterations^[8]
• Works at Windsor Castle
• Gothic Ballroom at Slane Castle, County Meath, Ireland
• Entrance lodge at Dromoland Castle, County Clare, Ireland
• Woolverstone Hall, Suffolk: extension and remodelling
• Rood Ashton House, Wiltshire: extension and remodelling; almost all demolished in the 1970s

• Penrhyn Castle, south front
• Penrhyn Castle, south front
• Penrhyn Castle, centre of west front
• Penrhyn Castle, east front
• The Drawing Room, Leigh Court
• The Conservatory exterior, Carlton House, London
• The Conservatory interior, Carlton House, London
• Garden front, Margam Castle
• West front, Margam Castle
• Lantern above main staircase, Margam Castle
• Main staircase, Margam Castle
• Main staircase, Margam Castle