Keiji Morokuma (諸熊 奎治, Morokuma Keiji; July 12, 1934 – November 27, 2017) was a Japanese theoretical chemist and chemical engineer known for developing energy decomposition analysis for molecular interactions[1] and the ONIOM method in quantum chemistry.

He stayed at Rochester until 1976 before moving to the Institute for Molecular Science in Okazaki, Japan and worked there until 1993.

In 1993, Morokuma moved back to the US and became the William Henry Emerson Professor of Chemistry at Emory University.

[8] He investigated potential surfaces in chemical reactions and reactions and structure of nanoparticles, proteins and transition metal complexes as well as photochemistry of excited state molecules and biomolecules.

In 1978, he received the Prize of the International Academy of Quantum Molecular Science, of which he was a member.