Gideon Mark Henderson FRS (born 1968) is a British geochemist whose research focuses on low-temperature geochemistry, the carbon cycle, the oceans, and on understanding the mechanisms driving climate change.

[1] Henderson is currently the Chief Scientific Adviser and Director General for Science and Analysis at the UK Government's Department for Environment, Food, and Rural Affairs (Defra).

After a brief stint at the journal Nature, Henderson was a postdoctoral fellow (1994-1996) and then associate research scientist (1996-1998) at the Lamont–Doherty Earth Observatory of Columbia University, where he worked with Wally Broecker and Bob Anderson.

Awards include European Union of Geosciences outstanding young scientist award (2001), the Philip Leverhulme Prize (2001), the Wollaston Fund of the Geological Society of London (2006), and the Plymouth Marine Science Medal (2016) In 2013 he was elected a Fellow of the Royal Society (FRS), his nomination read: "Gideon Henderson has developed new techniques for determining the timescales, magnitude and effects of past global climate change.

With new approaches to dating sediments he showed that certain glacial cycles are inconsistent with models of orbital forcing and was able to quantify weathering fluxes.