Tohru Eguchi (江口 徹, February 2, 1948 – January 30, 2019)[1] was a Japanese theoretical physicist.

While at SLAC in 1978, Eguchi and  Andrew J. Hanson discovered an exact Euclidean instanton solution[2] of the vacuum equations of general relativity, the Eguchi–Hanson space metric.

[3][4][5] This solution has applications, for example, in the construction of smooth compact Calabi–Yau manifolds in superstring theory.

[6] In the early 1980s, he published an influential and widely cited review article on differential geometric methods in physics with Andrew J. Hanson and Peter Gilkey.

[7] They extensively treated the physical applications of the Atiyah-Singer index theorem and related mathematical results.