Jannasch is a German surname. Notable people with this surname include the following: Holger W. Jannasch (1927-1998), German microbiologist for whom the genus Jannaschia was named Lilli Jannasch (1872–1968), German feminist, pacifist, journalist and graphologist Marie Jannasch (1824–1877), German nurse Niels Jannasch (1924–2001), German-Canadian mariner and marine historian Wilhelm Jannasch (1888–1966), German Protestant theologian and clergyman