Takeshi Oka (岡 武史, Oka Takeshi, born 1932), FRS FRSC, is a Japanese-American spectroscopist and astronomer specializing in the field of galactic astronomy, known as a pioneer of astrochemistry and the co-discoverer of interstellar trihydrogen cation (H+3).He is now R.A. Milliken Distinguished Service Emeritus Professor, Departments of Astronomy and Astrophysics, Chemistry; Enrico Fermi Institute; and the College of University of Chicago.