James Moran is an American radio astronomer living in Massachusetts, USA.

He was a professor of Astronomy at Harvard University from 1989 through 2016, a senior radio astronomer at the Smithsonian Astrophysical Observatory from 1981 through 2020 and the director of the Submillimeter Array during its construction and early operational phases from 1995 through 2005.

Dr. Moran is perhaps best known for his VLBI studies of 22 GHz water maser emission from the nucleus of the galaxy NGC 4258 (M106).

Monitoring of the proper motion of the individual maser spots in the black hole's accretion disk allowed a direct measurement of the distance to NGC 4258, which provided an important calibrator for the use of Cepheid variable stars as distance indicators.

[4] Dr. Moran wrote, along with Richard Thompson and George Swenson, a comprehensive graduate-level textbook on radio interferometry: Interferometry and Synthesis in Radio Astronomy, the third edition of which was published in 2017.