This is a proceedings volume of an international conference 'Operator Algebras and Mathematical Physics' held at Tohoku University in August, 2016. This meeting was the 9th MSJ-Seasonal Institute of the Mathematical Society of Japan. Twenty-eight researchers gave lectures on a wide range of topics on operator algebras and their applications to mathematical physics. This volume contains one survey article and 11 research articles based on the lectures given. We recommend this to researchers and graduate students in related fields strongly.Published by Mathematical Society of Japan and distributed by World Scientific Publishing Co. for all markets except North America