1840 births

Émile Nouguier (17 February 1840 – 23 November 1897) was a French civil engineer and architect. He is famous for co-designing the Eiffel Tower, built 1887–1889 for the 1889 Universal Exposition in Paris, France, the Garabit viaduct, the highest in the world at the time, near Ruynes-en-Margeride, Cantal, France, and the Faidherbe Bridge over the Sénégal River in Senegal.
In 1861 he attended and graduated the École Polytechnique in Paris, in 1862 he joined the École nationale supérieure des mines de Paris from which he graduated in 1865 with the title of mining construction engineer.

Camille Alphonse Faure (21 May 1840, Vizille – 14 September 1898) was a French chemical engineer who in 1881 significantly improved the design of the lead-acid battery, which had been invented by Gaston Planté in 1859. Faure's improvements greatly increased the capacity of such batteries and led directly to their manufacture on an industrial scale. The patents were assigned to the Société La Force et la Lumière. The right to use these patents in the British Isles were sold to the Faure Electric Accumulator Company on 29 March 1881. Faure was a consultant engineer with William Edward Ayrton for this company.

Joseph Jean Baptiste Neuberg (30 October 1840 – 22 March 1926) was a Luxembourger mathematician who worked primarily in geometry.

Jacques Raphaël Lépine (6 July 1840 – 17 November 1919) was a French physiologist who was a native of Lyon.

Albert Bythesea Weigall CMG, (16 February 1840 – 20 February 1912) was an English-born Australian schoolmaster, headmaster of Sydney Grammar School for 45 years.

Louis van Waefelghem (13 January 1840, in Bruges – 19 June 1908, in Paris) was a Belgian violinist, violist and one of the greatest viola d'amore players of the 19th century. He also composed several works and made transcriptions for viola and viola d'amore.
Waefelghem was educated at the Athénée Royal in Bruges and then studied violin with Lambert Joseph Meerts at the Koninklijk Conservatorium in Brussels. After finding success as a violinist in Germany and at the Opera House in Budapest, he moved to Paris in 1863 to pursue a career as a performer on viola and viola d'amore. He played in the orchestra of the Paris Opera in 1868 and also in the Pasdeloup Orchestra. Waefelghem was Examiner of the Viola at the Conservatoire de Paris before Théophile Laforge was appointed the first Professor of Viola in 1894. His reputation as a gifted violist quickly spread and, after the Franco-Prussian War (1870–1871), he traveled to London where he played in the Royal Opera orchestra and at chamber concerts of the Musical Union with Joseph Joachim, Leopold Auer, Henri Vieuxtemps, Camillo Sivori, Pablo de Sarasate, and others. From 1875 he was the violist of the Quatuor Marsick, along with Guillaume Rémy, Jules Delsart and founder Martin Pierre Marsick, one of the best and most famous string quartets in Paris of the time. He also a member of the Quatuor Geloso and of Ovide Musin's quartet with Metzger and Vander Gucht. Waefelghem was the principal violist with the Orchestre Lamoureux from 1881 to 1895.
In 1895 Waefelghem, along with colleagues Laurent Grillet (hurdy-gurdy), Louis Diémer (harpsichord) and Jules Delsart (viola da gamba), founded the Société des Instruments Anciens. The ensemble gave their début at the Salle Pleyel in Paris on 2 May 1895 and performed throughout Europe with great success. Thereafter Waefelghem devoted himself entirely to the revival and study of the viola d'amore. He quickly became one of the greatest viola d'amore players of the 19th century, and being a highly enthusiastic researcher, restored to the world the complete library of music for the instrument which had sunk into oblivion.

Désiré-Magloire Bourneville (English: ) (20 October 1840 – 28 May 1909) was a French neurologist born in Garencières.

Henri Didon (17 March 1840, in Le Touvet – 13 March 1900, in Toulouse) was a famous French Dominican preacher. He was also a writer, educator, and a promoter of youth sports. His outsize personality often put him in conflict with his religious hierarchy.
He coined the term Citius, Altius, Fortius for an 1891 youth sports competition he organized in Arcueil and that his friend Pierre de Coubertin was assisting. The latter proposed it as the official motto of the IOC in 1894.

Jules Cotard (1 June 1840 – 19 August 1889) was a French physician who practiced neurology and psychiatry. He is best known for first describing the Cotard delusion, a patient's delusional belief that they are dead, do not exist or do not have bodily organs.

Jacques Ludovic Trarieux (30 November 1840 in Aubeterre-sur-Dronne, Charente – 13 March 1904) was a French Republican statesman, lawyer, prominent Dreyfusard, and pioneer of international human rights.