Olateju Oyeleye (7 April 1924 – July 2013) was born in Ilesha, Osun State, Nigeria. He was the son of a farmer, Pa Joseph Oyeleye Aare, whose main produce was cocoa, kolanut, and bitter kola. His mother, Madam Felicia Esan Oyeleye, was a "petty trader" who hawked beans and pap. His early childhood was the foundation of his religious life and core values, where his parents through example developed his faith in God, "respect for others, desire for service, and passion for excellence". Teju Oyeleye attended Peter's Anglican Primary School, the equivalent to Elementary School in North America. He later attended Ilesha Grammar School, where he graduated in 1942. He had several important role models growing up. His older brother, Daniel Babalola Oyeleye, got him his first job after high school at the Nigerian Post and Telegram, or P&T, organisation, where he worked for about 10 years. His older brother also encouraged him to follow his passion for science. While working at P&T, he developed a fascination for morse code and the science around how the telegraph key worked. Another mentor was the cousin of a good friend who was a teacher at Yaba Technical College. The cousin's explanation of how a telegraph key functioned and the relationship between electricity and magnetism was crucial in his selecting Electrical Engineering in college. A final role model for Teju was Mr. Joseph Onawumi, who encouraged him with his GCE Advanced level classes (the equivalent to AP classes) in Physics, Chemistry, and Mathematics and assisted him with his application to the University of London.