Oncken is a surname. Notable people with the surname include:
Arthur Oncken Lovejoy, a German-born American philosopher August Oncken (1844–1911), a German economist (German article) Hermann Oncken (1867–1945), a German historian Johann Gerhard Oncken (1800–1884), a pioneer German Baptist preacher Wilhelm Oncken (1835–1905), a German historian
See also Onken (disambiguation)