Sir Thomas Leon Blundell, FRS FRSC FMedSci MAE (born 7 July 1942) is a British biochemist, structural biologist, and science administrator.

Blundell has made contributions to the structural biology of polypeptide hormones, growth factors, receptor activation, signal transduction, and DNA double-strand break repair, subjects important in cancer, tuberculosis, and familial diseases.

His speciality is molecular biology and his research on identifying the chemical processes of diseases has led to the development of drugs to treat Aids, cancer, cataracts and diabetes.

[17] Blundell's research interests lie in elucidating the architecture and function of macromolecules and their multi-component assemblies using methods from biochemistry, protein crystallography, and bioinformatics, with the objectives of understanding biological function, of knowledge-based prediction of structure, and of discovering new therapeutics for cancer and tuberculosis.

[2][11] Systems studied include DNA repair, hormones, growth factors and hormone/receptor interactions, cellular signalling, crystallins (lens proteins), renin and HIV protease.

At least seven of the Molecule-of-the-Month features at the RCSB site of the worldwide Protein Databank have featured molecular structures solved and studied by the Blundell lab, such as the glucagon hormone shown at left in David Goodsell's drawing,[18][19] nerve growth factor,[20][21] the RAD51-BRCA2 DNA recombination complex,[22][23] and the DNA ligase shown at right.

Blundell has supervised numerous Doctor of Philosophy students and postdoctoral researchers in his lab including Tim Hubbard,[4] Laurence Pearl,[5] Andrej Šali,[6] and Charlotte Deane.

His work on avian pancreatic polypeptide, the acid proteinases from mammals and fungi and the proteins of the eye lens is characterised by similar extensive detail from which he disects [sic] important structural relationships and derives principles and guides on protein evolution and hormone (especially growth hormone) function.

He has been awarded Honorary Doctorate degrees from 16 universities and was interviewed by Kirsty Young on the BBC Radio 4 programme Desert Island Discs in 2007.