Thomas G. Alexander is a professor emeritus of Brigham Young University. He was born in Logan, Utah, and served a mission for The Church of Jesus Christ of Latter-day Saints in the West German Mission. In 1959, he married Marilyn Johns, with whom he had five children.

He earned his AA in 1955 at Weber State University and his BS in 1960 and MA in 1961 from Utah State University. In 1965, Alexander received his PhD in American history from the University of California, Berkeley. Alexander joined the BYU history faculty in 1964, where he taught Utah history and American environmental history. He received BYU's highest faculty award, the Karl G. Maeser Distinguished Faculty Lecturer Award. In 2001, he received the Emeriti Alumni Lifetime Achievement Award from Weber State University. Alexander retired from full-time teaching at BYU in 2004.

Alexander was president of the Mormon History Association from 1974 to 1975. He was also president of the Pacific Branch of the American Historical Association; president and fellow of the Utah Academy of Sciences, Arts, and Letters; president of the Association of Utah Historians; chair of the Utah Board of State History; chair of the Utah Humanities Council; national president of Phi Alpha Theta, the history honor society; fellow of the Utah State Historical Society; and chair of BYU's Faculty Advisory Council. In 2004, after his retirement, he served an LDS Church Educational System mission in Berlin, Germany, with his wife.