Dr. Walter C. Langsam, a historian who was former president of the University of Cincinnati and Wagner College on Staten Island, died today after a long illness. He was 79 years old. Dr. Langsam was the author of 15 books, including ''The World Since 1914,'' first published in 1933, an academic best-seller through eight editions. Dr. Langsam was president of the University of Cincinnati from 1955 to 1971 and guided the institution through a period of enormous growth. In his administration, the university's enrollment grew from 14,000 to 35,000 and the annual operating budget increased from $10 million to $102 million. He also headed Wagner College from 1945 to 1952. Born Jan. 2, 1906, and reared in New York City, Dr. Langsam received his doctoral degree from Columbia University in 1930. He taught at Columbia from 1927 to 1938. He taught at Union College in Schenectady, N.Y., from 1938 to 1945, and was president of Gettysburg College in Pennsylvania from 1952 to 1955.