Keisai Aoki (????, Aoki Keisai, April 8, 1893 – March 6, 1969) was a Japanese missionary who paved the way to the establishment of Hansen's disease (leprosy) sanatorium Kunigami-Airakuen, Okinawa, now Okinawa Airakuen Sanatorium, Japan.
At the age of 16 he developed leprosy and later, under the guidance of Hannah Riddell, he also helped people with leprosy in Okinawa.