Gerrit Grijns (May 28, 1865 – November 11, 1944), was a Dutch researcher and co-discoverer of vitamin B1 (thiamine) as the successor to the later Nobel Prize winner Christiaan Eijkman.

It was Eijkman who in the former Dutch East Indies was the first to associate the deficiency disease beriberi with the lack of the outer membrane in machine-peeled rice.

His successor Grijns believed that the membrane contains a substance that is indispensable for a healthy metabolism.

By writing of "partial hunger" and "protective substance" in 1901, Grijns anticipated the concept of vitamins.

After returning to the Netherlands, Grijns became professor of animal physiology at Wageningen University in 1921, where he taught and conducted research until 1935.