Johann Conrad Barchusen, originally Barkhausen, sometimes Barchausen (16 March 1666 Horn, Principality of Lippe - 2 October 1723, Utrecht) was a pharmacist, chemist, physician and professor.

After the death of his parents, Johann Conrad Barchusen lived with his uncle Franz Caspar Barkhausen (1636-1715).

[5][6] On 16 September 1694 the city council of Utrecht granted Barchusen the right to teach private chemistry courses which could be attended by students of the university.

[1] His courses were so successful that the magistrate, by decision of 8 April 1695, financed construction of a chemical laboratory in the bastion of what was then the fortress of Sonnenborgh.

[2][4] On 13 December 1699 Barchusen married Maria Johanna Pijlsweert[9] (variously Pylsweert, d. 1717), daughter of a wealthy Utrecht family.

[1][4] His viewpoint was broader than most of his contemporaries, placing chemistry in the context of natural philosophy and the composition of matter, rather than medicine.

[10][1] Barchusen emphasized methods and laboratory techniques, describing in detail the tasks which a chemistry student should be able to carry out: the use of fires and specific procedures such as distillation, incineration, putrefaction, evaporation and fermentation to examine mixtures of the four substances and their chemical composition.

He is an honest writer, and sufficiently accurate; he delivers good matter in an excellent style, tho' his reasonings are not so much to our mind.

– Herman Boerhaave, A new method of chemistry (London, 1727), p. 39[7]Barchusen and his students carried out analytical investigations of blood, urine, feces, and bile, all of which were considered important to medical practice.