Josiah Willard Gibbs Sr. (30 April 1790 – 25 March 1861) was an American linguist and theologian, who served as professor of sacred literature at Yale University.

He was eventually promoted to a professorship at Yale Divinity School's department of sacred literature, a job that he continued to occupy until his death.

[2] His work increasingly emphasized linguistics and was influenced strongly by the grammar of James Harris and by German scholars such as Wilhelm Gesenius and Karl Becker.

By visiting the African passengers in jail and showing them piles of pennies, he was able to learn to count to ten in the language spoken by most of them, which was determined to be Mende.

In this way he eventually met two British sailors, James Covey (a former slave) and Charles Pratt, who recognized the words and could serve as interpreters.

Gibbs and Day testified as expert witnesses during the trial, establishing that the claim by the owners of the Amistad ship that the black passengers were slaves born in Cuba was false.