Sarah Thomas came to Cornell University in August 1996 as the Carl A. Kroch University Librarian. In a career spanning thirty years, Thomas has cataloged books in Harvard University's Widener Library, taught German at the Johns Hopkins University, managed library coordination at the Research Libraries Group in California, held a Council on Library Resources Management Internship at the University of Georgia, served as the Associate Director for Technical Services at the National Agricultural Library, and directed both the Cataloging Directorate and the Public Service Collections Directorate at the Library of Congress. At Cornell she provides leadership for the twenty libraries that make up the University's library system. The Cornell University Library holds over 7 million volumes and has an active digital library program. The Library received the 2002 ACRL for Excellence in Academic Libraries Award.

Thomas has had a long-standing interest in issues relating to digital libraries. She is a member of the Board of the Digital Library Federation. She is a past president of the Association of Research Libraries. She speaks frequently on the future of libraries, digital archiving, new forms of scholarly communication, and on the relationship between library architecture and traditional and emerging functions of libraries. She is the principal force behind Project Euclid, a user-centered initiative to create an online environment for the effective and affordable distribution of serial literature in mathematics and statistics. An outgrowth of Project Euclid is DPubS, an open source digital publishing system, for which Thomas also serves as principal investigator.

Thomas earned a Ph.D. in German literature from The Johns Hopkins University in 1983, writing her dissertation on the topic: "Hugo von Hofmannsthal and the Insel-Verlag: a Case Study of Author-Publisher Relations." She received her bachelor's degree from Smith College in 1970 and a Master of Science in Library Science from Simmons College in 1973.