B. C. P. Jansen (1 April 1884, Zwolle – 18 October 1962) was a Dutch chemist and biochemist.
In the Dutch Indies[chronology citation needed], with his colleague W. F. Donath, he isolated in crystalline form an anti-beriberi factor (known as vitamine B1 or aneurin) from rice polishings and named it thiamine (sulfur-containing amine).
[1] It was the first vitamine to be obtained in pure form.
Jansen was elected a corresponding member of the Royal Netherlands Academy of Arts and Sciences in 1927, he resigned in 1929.
He was re-admitted as member in 1946.