English chemist whose most important contribution was his study of nitrogen fertilizers and their effects on crops.

In 1843 Gilbert joined Sir John Bennet Lawes (Lawes, Sir John Bennet, 1st Baronet) as co-director of agricultural research at the newly founded Rothamsted Experimental Station, Hertfordshire, the first organized agricultural experiment station in the world. Their collaboration lasted for more than half a century. In the 1840s they initiated the manufacture of superphosphate fertilizer, one of their inventions. From 1884 to 1890 Gilbert was Sibthorpian professor of rural economy at Oxford University. He was knighted in 1893.