Onderdonk is a surname. Notable people with the surname include:
Andrew Onderdonk (1848–1905), construction contractor Benjamin T. Onderdonk (1791–1861), bishop of the Episcopal Diocese of New York Henry Onderdonk (1789–1858), second Episcopal bishop of Pennsylvania Julian Onderdonk (1882–1922), American Impressionist painter Robert Jenkins Onderdonk (1852–1917), American painter and art teacher Virginia Onderdonk (1908–1994), American philosopher and college dean William H. Onderdonk (1820–1882), American lawyer