Arnulfo Duenes Trejo (August 15, 1922 – July 5, 2002) was a writer and Professor of Library Science at the University of Arizona.

He was a leader in the movement to increase library collections of Latino literature and Spanish-language materials in the United States.

He moved to the United States at the age of three, gaining American citizenship in 1944 during his service with the U.S. Army during World War II with the 143 Infantry Division in the South Pacific.

When he started his position as a Professor of Library Science at the University of Arizona in 1965, Trejo was one of only five Hispanic librarians in the nation.

During the institute's four-year existence Trejo was directly involved in recruiting Latino students into the program and contributed to their education.