Born in Spokane, Washington, Nellis was raised in northwestern Montana and graduated from Libby High School in 1972.
He created the President's Diversity Council, enhanced what became a nationally award-winning engagement effort through creation of the Office for Community Partnerships, improved major inter-disciplinary initiatives, and significantly improved business partnerships between the university and business and commodity groups in Idaho and throughout the Northwest.
[18] On March 22, the Texas Tech Board of Regents unanimously confirmed him as the university's next president, effective June 15.
He has advocated for continued quality enrollment growth (including stronger advocacy for national and international student recognition), accelerated research expenditures and faculty recognitions, creating a more engaged institution while promoting industry and community partnerships, with a commitment toward global connections and creativity while seeking external revenue sources to invest in the university enterprise.
[23] Evidence suggests that this reinforcing of academic excellence improved Ohio University's ranking and incoming student GPA scores since 2018.
[24] He served as a member of the Association of Public and Land-grant Universities Commission on Economic and Community Engagement Executive Committee in 2019.
The faculty senate accused Nellis of "leading the university to a budget crisis, made much worse by the coronavirus pandemic.
[28] Nellis was named 2023 Fellow of the American Association of Geographers, a lifetime achievement award recognizing his expertise in the field of geography, particularly remote sensing, and his leadership roles in higher education.