Nancy Roos (February 28, 1905 – April 6, 1957) was a U.S. chess champion.
She was born as Nanny [sic] Krotoschin in Berlin, which was then a part of Prussia, to Georg Krotoschin and Martha Cohn Krotoschin, who were part of a large Jewish family that had lived in Berlin for generations. She married Martin Roos, who had been born in 1903 in Amsterdam, Netherlands.
She took second at the Pan-American Tournament in 1954 behind Mary Bain and Mona May Karff, and tied for second at the 1942 U.S. Women's Championship behind Adele Belcher and Karff.