Charles K. Kao, an international pioneer of optical communications and Nobel laureate, passed away on September 23, 2018 at the age of 84. Charles K. Kao was born in Shanghai in 1933 and graduated from Woolwich Polytechnic in London in 1957 with a degree in electrical engineering and physics. He taught and conducted research in the UK for nearly a decade, before coming to Hong Kong in 1967 to take up a post at the then-University of Hong Kong (HKU). With his research group at HKU, Professor Kao was the first to demonstrate that optical fibers could be used to transmit pocket-to-point signals without significant attenuation, a discovery that revolutionized modern communication. His optical fiber research was awarded the Nobel Prize in Physics in 2009. In addition to the Nobel Prize, Professor Kao was also an esteemed alumnus of the University of London and an honorary professor of several universities in mainland China, Hong Kong, and Taiwan. He was a fellow of the Royal Society, a foreign member of the Chinese Academy of Sciences, and three scientific societies in the United Kingdom and the United States of America. Throughout his career, Professor Kao championed scientific advancement, Asia-Pacific scientific exchanges, and the coordination of science and technology in society. He published numerous books and papers, and received extensive awards and recognitions for both his scientific achievements and his public service, including a knighthood in 2004 for his technical contributions to telecommunications in the United Kingdom. He is survived by his extended family and loved ones.