Baron Nicholas Genrikhovich Hartwig (Russian: ??????? ?????????? ???????) (December 16, 1857 – July 10, 1914) was an Imperial Russian diplomat who served as ambassador to Persia (1906–1908) and Serbia (1909–1914).
An ardent Pan-Slavist, he was said to be "more Serbian than the Serbs" and in the period prior to World War I was thought by many to practically control the foreign policy of the Serbian government.
He encouraged Serbia to stand up to Austria-Hungary and may therefore be seen as one of the causes of the war.