Klas Bernhard Johannes Karlgren (15 October 1889 – 20 October 1978) was a Swedish
sinologist and
linguist who pioneered the study of
Chinese historical phonology using modern comparative methods. In the early 1900s, Karlgren conducted large surveys of a number of Chinese dialects and studied historical information on rhyming in ancient Chinese poetry, then used them to create the first ever complete
reconstructions of what is now called
Middle Chinese and
Old Chinese.