Hiroshi Nishihara (西原寛, Nishihara Hiroshi), born 21 March 1955, is a Japanese chemist and Professor of Chemistry at The University of Tokyo in Japan.

Currently heading the department of Chemistry and Inorganic Chemistry Laboratory in The University of Tokyo, he is a distinguished professor, researcher and pioneer in the field of synthesis and electrochemistry of conductive metal complex polymers.

His research is focused on creation of new electro- and photo-functional materials comprising both transition metals and π-conjugated chains, and invention of unidirectional electron transfer systems utilizing molecular layer interfaces.

He is presently a Vice President of The Electrochemical Society of Japan, and the regional representative of Japan for International Society of Electrochemistry (ISE).

Coordination Chemistry, Organometallic Chemistry, Electrochemistry, Photochemistry, Nanomaterials