Timothy Michael Lenton OBE FGS FLS FRSB (born July 1973) is Professor of Climate Change and Earth System Science at the University of Exeter. He was awarded a Royal Society Wolfson Research Merit Award in 2013.

He graduated with a first-class degree in natural sciences from Robinson College, Cambridge in 1994 and completed his PhD under Andrew Watson at the University of East Anglia in 1998.

Lenton has taken an interest in the Gaia hypothesis for much of his career. Early in his career, in the journal Nature, Lenton addressed a concern that the Gaia hypothesis was incompatible with the theory of natural selection by demonstrating that a model based on Daisyworld was strengthened by incorporating natural selection. In the same year, Lenton co-authored the paper "Spora and Gaia" with W. D. Hamilton, proposing that marine algae's tendency to release dimethyl sulfide, which in turn acts as a chemical precursor for cloud condensation nuclei, is an adaptive trait, as the algae can use the clouds to disperse themselves around the world. Lenton, with Andy Watson, co-authored the book Revolutions that Made the Earth; it expands on the ideas of James Lovelock on the Gaia hypothesis, by highlighting mechanisms by which the Earth system has been stabilised by negative feedbacks throughout Earth history.

Lenton has participated in studies of possible population displacement due to climate change.

Lenton has been called 'a leading tipping point expert'.

Lenton was awarded the OBE in the 2025 Birthday Honours, for services to understanding climate tipping points.