Thomas Cubitt (25 February 1788 – 20 December 1855) was a British master builder, notable for his employment in developing many of the historic streets and squares of London, especially in Belgravia, Pimlico and Bloomsbury.

The son of a Norfolk carpenter, he journeyed to India as a ship's carpenter, from which he earned sufficient funds to start his own building firm in 1810 on Gray's Inn Road, London, where he was one of the first builders to have a 'modern' system of employing all the trades under his own management.

Cubitt's first major building was the London Institution in Finsbury Circus, built in 1815. After this he worked primarily on speculative housing at Camden Town, Islington, and especially at Highbury Park, Stoke Newington.

His development of areas of Bloomsbury, including Gordon Square and Tavistock Square, began in 1820, for a group of landowners including the Duke of Bedford.

Cubitt's work outside London includes the country house Polesden Lacey, near Dorking, Surrey, which he rebuilt to largely its present form in the early 1820s.

He was commissioned in 1824 by Richard Grosvenor, 2nd Marquess of Westminster, to create a great swathe of building in Belgravia centred on Belgrave Square and Pimlico, in what was to become his greatest achievement in London. Notable amongst this development are the north and west sides of Eaton Square, which exemplify Cubitt's style of building and design.

After Cubitt's workshops in Thames Bank were destroyed by fire, he remarked "Tell the men they shall be at work within a week, and I will subscribe £600 towards buying them new tools."

Cubitt was employed in the large development of Kemp Town in Brighton. His public works included the provision of public parks, including being an organiser of the Battersea Park Scheme.