Iain Simpson Stewart MBE FGS FRSE (born 1964) is a Scottish geologist who is currently Jordan-UK El Hassan bin Talal Research Chair in Sustainability at the Royal Scientific Society in Jordan. He is a UNESCO Chair in Geoscience and Society and formerly a member of the Scientific Board of UNESCO's International Geoscience Programme. Described as geology's "rock star", Stewart is best known to the public as the presenter of a number of science programmes for the BBC, notably the BAFTA nominated Earth: The Power of the Planet (2007).