Jun-iti Nagata (長田 潤一, Nagata Jun'ichi, 1925 - 6 November 2007) was a Japanese mathematician specializing in topology.

In 1956, Jun-iti Nagata earned his PhD from Osaka University under the direction of Kiiti Morita.

He was the author of two standard graduate texts in topology: Modern Dimension Theory[1] and Modern General Topology.

[2] His name is attached to the Nagata–Smirnov metrization theorem, which was proved independently by Nagata in 1950 and by Smirnov in 1951, as well as the Assouad–Nagata dimension of a metric space, which he introduced in a 1958 article.

[3] Nagata became a professor emeritus at both Osaka Kyoiku University, where he taught for 10 years, and Osaka Electro-Communication University, where he taught for 5 years.