Johann Gasteiger (27 October 1941 in Dachau) is a German Chemist and a Chemoinformatician on which he wrote and edited various books.

He obtained his PhD in Organic Chemistry at Ludwig Maximilian University of Munich in 1971 with Professor Rolf Huisgen.

In 1997, Johann Gasteiger founded the company Molecular Networks, which distributes software developed at the Computer-Chemie-Centrum.

His main research interest is the development of software for drug design (for example via QSAR, the simulation of chemical reactions, for synthesis planning in organic chemistry, machine learning for spectroscopy, and the application of neural networks and genetic algorithms in chemistry.

In 1979, Johann Gasteiger and Mario Marsili published a method for the iterative calculation of atomic partial charges in molecules.