George Bellas Greenough (January 18, 1778 - April 2, 1855) was an English geologist.

Greenough was born in London. He was educated at Eton, and afterwards (1795) entered Pembroke College, Oxford, but never graduated. In 1798 he proceeded to Gottingen to prosecute legal studies, but having attended the lectures of Blumenbach he was attracted to the study of natural history, and, coming into the possession of a fortune, he abandoned law and devoted his attention to science. He studied mineralogy at Freiburg under Werner, travelled in various parts of Europe and the British Isles, and worked at chemistry at the Royal Institution. A visit to Ireland aroused deep interest in political questions, and he was in 1807 elected member of parliament for the borough of Gatton , continuing to hold his seat until 1812. Meanwhile his interest in geology increased, he was elected F.R.S. in 1807, and he was the chief founder with others of the Geological Society of London in 1807. He was the first chairman of that Society, and in 1811, when it was more regularly constituted, he was the first president: and in this capacity he served on two subsequent occasions, and did much to promote the advancement of geology. In 1819 he published A Critical Examination of the First Principles of Geology, a work which was useful mainly in refuting erroneous theories. In the same year was published his famous Geological Map of England and Wales, in six sheets; of which a second edition was issued in 1839. This map was to a large extent based on the original map of William Smith; but much new information was embodied. In 1843 he commenced to prepare a geological map of India, which was published in 1854. He died at Naples.