Thomas Christian Südhof (German pronunciation: [ˈtoːmas ˈzyːtˌhoːf] ⓘ; born December 22, 1955), ForMemRS, is a German-American biochemist known for his study of synaptic transmission.

Currently, he is a professor in the school of medicine in the department of molecular and cellular physiology, and by courtesy in neurology, and in psychiatry and behavioral sciences at Stanford University.

In Göttingen Südhof worked on his doctoral thesis, in which he described the structure and function of chromaffin cells, at the Max Planck Institute for Biophysical Chemistry in the lab of Victor P. Whittaker.

During his postdoctoral research fellowship, Südhof worked to describe the role of the LDL receptor in cholesterol metabolism, for which Brown and Goldstein were awarded the Nobel Prize in Physiology or Medicine in 1985.

Südhof described the structure and function of chromaffin cells which are responsible for the release of epinephrine, norepinephrine and endorphins from the medulla of the adrenal gland.

After completing his thesis in 1983, Südhof moved to UT Southwestern Medical Center for his postdoctoral training where he began researching in the department of molecular genetics under the supervision of Joseph L. Goldstein and Michael Stuart Brown.

Briefly continuing work with Goldstein and Brown, Südhof helped identify a DNA element in the LDL gene that produced sterol mediated end-product repression when inserted in a viral promoter.

Discovery of sterol regulatory elements and LDL receptor function led to the subsequent development of statin derived cholesterol medications such as atorvastatin (Lipitor)—the top-selling branded pharmaceutical drug in the world in 2008.

After binding calcium ion to a region in its cytosolic domain, vesicular synaptotagmin promotes quick or slow neurotransmitter release from the presynaptic neuron via interaction with regulatory and fusion related proteins such as members of the SNARE complex.

Südhof also discovered RIMs and Muncs (most notably Munc13 and Munc18), soluble proteins which aid in the fusion of neurotransmitter vesicles to the nerve cell membrane and play an important role in synaptic plasticity.

Südhof was also responsible for elucidating the action of tetanus and botulinum toxins, which selectively cleave synaptobrevin and SNAP25, respectively, inhibiting vesicle fusion with the presynaptic membrane.

Südhof's research has not only given the scientific community a great understanding of the processes underlying synaptic transmission and synapse formation, but has also advanced medical knowledge of mechanisms behind poorly understood diseases such as Alzheimer's, Schizophrenia, and Autism.

also engages in scientific ethics as exemplified by his recent work at PLOS Biology Truth in Science Publishing: A personal Perspective[13] and various interviews including his discussion about music, policy and medicine with The Lancet.