Thomas Broun (né Brown; 15 July 1838 – 24 August 1919) was a Scottish-born soldier, farmer, teacher and entomologist, who spent much of his career in New Zealand.

His most significant scientific work, the Manual of the New Zealand Coleoptera, was published in seven volumes from 1880, though he remained an amateur until the 1890s, when he was appointed as a government entomologist and as an inspector of imported fruits.

[5] He joined the Forfar Militia Artillery around 1854;[b] on 8 July 1856, at which point he held the rank of first lieutenant, he transferred without purchase as an ensign to the regular army's 35th (Sussex) Regiment of Foot, which was engaged in the Crimean War.

[6] After the end of the war in 1856, the regiment was deployed to Burma, where Broun took an interest in the region's brightly-coloured tropical insects and began to collect specimens to send to the British Museum in London.

On the advice of Theodore Haultain, New Zealand's Defence Minister,[2] Broun took a job in 1876 as a teacher in Tairua on the Coromandel Peninsula,[1] which became one of his favourite locations to collect specimens.

[1] Broun began his amateur entomological work in New Zealand shortly after his departure from the army,[2] and presented his first academic paper to the Auckland Institute in 1875.

[1] His collecting activity intensified after 1876, when he began teaching in Tairua: he started sending specimens to the entomologist David Sharp in London for description.

[4] In 1878, he moved to Parua Bay on the northern side of Whangarei Harbour, where he began to prepare the first volume of his Manual of the New Zealand Coleoptera;[16] it was published in 1880 via the Colonial Museum and Geological Survey of Wellington.

[17] He bought farmland near Drury in South Auckland, in 1889, and commissioned the architect John Stoupe to build a house there, which Broun called by the Māori name Nga Oki ('The Oaks') after the trees he had planted there.

[24] Broun gained little financially from his scientific work, but was elected as an honorary member of various European learned societies and Australian naturalists' clubs in recognition of it.

[25] The entomologist John Charles Watt described Broun's collecting as "intensive rather than extensive", noting that he appears never to have visited New Zealand's South Island.

[27] While the scale of Broun's duplications has not been concretely established, he is known to have listed the ground beetle Megadromus meritus under fifteen different names, at least five of which were based on studying only a single purported specimen.

[28][29] The entomologist Rowan Emberson has identified this habit of duplication, which he calls the "Broun effect", as a major reason behind the huge difference in reported beetle species between New Zealand and Great Britain: the number of identified Coleoptera species in New Zealand is 80% greater than that of Great Britain, while the numbers of other insect orders, such as Hemiptera ('true bugs') and Diptera (flies), are broadly similar.