Gart Westerhout (15 June 1927 – 14 October 2012) was a Dutch-American astronomer.[1] Well before completing his university studies at Leiden, he had already become well-established internationally as a radio astronomer in the Netherlands, specializing in studies of radio sources and the Milky Way Galaxy based on observations of radio continuum emissions and 21-cm spectral line radiation that originates in interstellar hydrogen. He emigrated to the United States, became a naturalized citizen, and held a number of important scientific and management positions in academic and government institutions.