John Turnbull Thomson was a civil engineer who played an instrumental role in the development of the early infrastructure of nineteenth century Singapore.

Thomson was born on 10 August 1821, at Glorum, Northumberland, England. He was the third child of Alexander Thomson and his wife, Janet, née Turnbull.

After his father was killed in a hunting accident in 1830, the young Thomson went to live with his mother in Abbey St. Bathans, Berwickshire. He was educated at Wooler and Duns Academy, later spending some time attached to Marischal College, Aberdeen, and Edinburgh University before studying engineering at Peter Nicholson's School of Engineering at Newcastle-on-Tyne.

Thomson arrived in the Malay Straits in 1838 and was employed by the East India Survey. In 1841 he was appointed Government Surveyor at Singapore and in 1844 became Superintendent of Roads and Public Works.

He was responsible for the design and construction of a number of notable engineering works including bridges, roads, and hospitals. He conducted the allotment survey of Singapore, the topographical survey of the island of Singapore and its dependencies, and the marine survey of the Straits of Singapore and the east coasts of Johore and Penang. His outstanding achievement was the erection of the Horsburgh Lighthouse on Pedra Branca Rock.

In 1853 his health failed and he returned to England where he studied modern engineering techniques, and travelled widely through Britain and the Continent inspecting engineering works. Early in 1857 he emigrated to New Zealand.

Thomson was a founder of the Otago and Southland Institutes of New Zealand, to which he contributed numerous papers on scientific subjects including ethnological studies. Through his knowledge of Hindustani and Malay, he became interested in comparative linguistics and developed a theory of racial diffusion based on philological evidence.

He was also a keen amateur painter of landscapes, working mostly in oils. His paintings have little artistic merit but from a topographical viewpoint are of some interest today.

Thomson married Jane Williamson of Dunedin in 1876. He died at his home on 16 October 1884.

During his government service in Singapore, Thomson was responsible for many projects:

• Thomson's 1852 report on Singapore's water supply led in 1862 to approval of the Thomson Reservoir, now MacRitchie Reservoir.
• He made an elaborate survey of the Straits of Singapore, in conjunction with Captain Congalton who was largely responsible for clearing pirates from Malayan waters. He also surveyed Keppel Harbour.
• He carried out repairs and lowering of the Coleman Bridge.
• He was the architect and builder of:
  • Horsburgh Lighthouse on Pedra Branca,
  • the spire for the St. Andrew's Cathedral,
  • Dalhousie Obelisk, a monument,
  • European Seaman's Hospital,
  • the first bridge across the Kallang River, known as Thomson Bridge, and
  • Tan Tock Seng Hospital at Serangoon Road.

Several extant places, roads and buildings in Singapore are named after J.T. Thomson. These include:

• Thomson, a region in central Singapore
• Thomson Road, which runs through the Thomson area