MOA-2009-BLG-266L is a Sun-like G-type star (about 0.56 solar masses, 5,778 K), 3,040 light-years from Earth. MOA-2009-BLG-266L b is a 10.4-Earth-mass planet, with an orbital period of 7.67 years, at 3.200 AU from its star, discovered in 2011 via microlensing. Microlensing detections occur when a foreground star's gravity briefly magnifies a background source, revealing planets that are otherwise too faint and distant to observe directly. MOA-2009-BLG-266L b circles in the outer system, comparable to the Jupiter region. Its low mass makes MOA-2009-BLG-266L b a Neptune- or super-Earth-class world rather than a gas giant.