Vitter spent sabbatical leaves at the Mathematical Sciences Research Institute in Berkeley, CA; INRIA in Rocquencourt, France; Ecole Normale Supérieure in Paris; Bell Laboratories in Murray Hill, New Jersey; Aarhus University in Aarhus, Denmark, and INRIA in Sophia Antipolis, France. On October 29, 2015, Vitter was unanimously named as the 17th chancellor of the University of Mississippi by the Mississippi Board of Trustees of State Institutions of Higher Learning (IHL). He began duties on January 1, 2016. He introduced a strategic plan named "Flagship Forward", with initiatives including a $1 billion building program, multidisciplinary research networks of faculty called Flagship Constellations, annual Technology Summits, major community partnerships through the M Partner program, and extended capacity and reach of the University of Mississippi Medical Center. The university began to look at Confederate symbols on campus and established an Office of Diversity and Community Engagement. In December 2018, the university's status as a Carnegie R1 research university was reaffirmed. In November 2018, Vitter announced that he would step down as chancellor to become a regular faculty member on January 4, 2019. Vitter is a computer scientist with over 350 books, journals, and conference publications, primarily on the design and mathematical analysis of algorithms dealing with big data and data science. His Google Scholar h-index is in the 70s, and he is an ISI highly cited researcher. He helped establish the field of I/O algorithms (a.k.a. "external memory algorithms") as a rigorous area of active investigation. He has also made fundamental contributions in databases; compressed data structures and indexing; data compression, including adaptive Huffman coding, arithmetic coding, image compression, and video compression; hashing and search data structures; randomized algorithms; sampling and random variate generation; prediction and machine learning; and average-case complexity. Vitter is a Fellow of the National Academy of Inventors (NAI) (2018), a Fellow of the American Association for the Advancement of Science (AAAS) (2009), a Fulbright Scholar (1998), a Fellow of the Association for Computing Machinery (ACM) (1996), a Fellow of the Institute of Electrical and Electronics Engineers (IEEE) (1993), a John Simon Guggenheim Memorial Foundation Fellow (1986), a National Science Foundation (NSF) Presidential Young Investigator Awardee (1985), and a member of Phi Kappa Phi (2017), Sigma Xi (1983), and Phi Beta Kappa (1977).