Koichi Tanaka (田中 耕一, Tanaka Kōichi, born August 3, 1959) is a Japanese electrical engineer who shared the Nobel Prize in Chemistry in 2002 for developing a novel method for mass spectrometric analyses of biological macromolecules with John Bennett Fenn and Kurt Wüthrich (the latter for work in NMR spectroscopy).

Tanaka graduated from Tohoku University with a bachelor's degree in electrical engineering in 1983, afterward he joined Shimadzu Corporation, where he engaged in the development of mass spectrometers.

The problem is that the direct irradiation of an intense laser pulse on a macromolecule causes cleavage of the analyte into tiny fragments and the loss of its structure.

In February 1985, Tanaka found that by using a mixture of ultra fine metal powder in glycerol as a matrix, an analyte can be ionized without losing its structure.

[5][6] This is because they first reported in 1985 a method, with higher sensitivity using a small organic compound as a matrix, that they named matrix-assisted laser desorption/ionization (MALDI).