Masataka Ogawa (小川 正孝, Ogawa Masataka, 21 February 1865 – 11 July 1930[1]) was a Japanese chemist mainly known for the claimed discovery of element 43 (later known as technetium), which he named nipponium.

In fact, he had discovered, but misidentified, element 75 (later called rhenium).

[2][3] After graduating from the University of Tokyo, he studied under William Ramsay in London, where he worked on the analysis of the rare mineral thorianite.

He extracted and isolated a small amount of an apparently unknown substance from the mineral, which he announced as the discovery of element 43, naming the newly discovered element nipponium.

[4] For this work, he was awarded a doctorate and the highest prize of the Tokyo Chemical Society.