Chihaya Adachi (born 26 October 1963) is a Japan-born scientist and lecturer specializing in organic electronics which is a field of materials science. Adachi is the Director of the Center for Organic Photonics and Electronics Research (OPERA) at Kyushu University, a large multi-disciplinary team of physicists, chemists, and engineers from both academia and industry.

Adachi is recognized as an innovator in the development of materials for organic light-emitting diodes (OLED). He has pioneered a new technology known as thermally activated delayed fluorescence (TADF).

In 2015, Adachi co-founded Kyulux in Fukuoka, Japan, to commercialize hyper-fluorescence TADF emitters, and he is a scientific advisor and ex-officio board member of Kyulux. Adachi also serves on Elsevier's Organic Electronics Editorial Board.