Born in Trewarthenick, Gregor was educated at Cambridge University. Although elected a fellow of his college he decided instead to pursue a career in the Church and became rector of Creed, Cornwall, in 1793.

In 1791 he found a strange black sand in Manaccan (then spelled Menacchan), Cornwall. This contained iron and manganese plus an additional substance that Gregor could not identify. He called it menacchanine and succeeded in extracting its reddish-brown oxide, which, when dissolved in acid, formed a yellow solution. Martin Klaproth isolated the same oxide from a different source in 1795 and demonstrated that it was a new element, naming it titanium.