Charles-Louis Barreswil (13 December 1817 – 22 November 1870) was a French physiologist and biochemist who was among the first to investigate the process of digestion in humans and also a range of other chemical applications including photographic and printing processes.
Barreswil studied chemistry under Pierre-Jean Robiquet (1780-1840) and Théophile-Jules Pelouze (1807-1867) in Paris.
Their approach was to feed a pure substance and examine if it was also produced in the urine or faeces.
In 1853, he worked along with Noël-Paymal Lebebours (1807-1873) and Rose-Joseph Lemercier (1803-1887) to develop a photo-lithographic method for etching and printing.
He gave up scientific research in 1865 and began to work on social problems, particularly on protection for young workers.