Konstantin "Kosta" Vojnović (Serbian pronunciation: [konstǎntin kôsta ʋǒːjnoʋit͡ɕ]; March 2, 1832 - May 20, 1903) was Serbian politician, university professor and rector in the Kingdom of Dalmatia and Kingdom of Croatia-Slavonia of the Habsburg Monarchy.
Vojnović was born in Herceg Novi (modern Montenegro) into the Serb Vojnović noble family. His grandfather Đorđe Vasiljević Vojinović (1760-1821) was a Russian military officer, he later returned to Boka Kotorska, and in 1800, in Ancona, he married Kasandra Angeli-Radovani from a Roman Catholic family. They had a son, Jovan. Count Jovan Đ. Vojinović (1811-1837) died at the age of 26, he married Katarina Gojković whose mother was of the family of Serbian Orthodox Metropolitan Stevan Stratimirović. Katarina later remarried to a Pelegrini. Jovan and Katarina had two sons, Konstantin (Kosta), and his brother Đorđe (Đura).
His brother Đorđe (1833-1895) was the mayor of Boka (1863-1877) and its representative deputy, and president of the Diet of Dalmatia in Zadar. As the people's deputy he fought against the Austrian politics that deliberately omitted the Bokan maritime affairs, which was the main occupation of his ancestors.
Konstantin and Đorđe were baptized in the Serbian Orthodox Savina monastery in Herceg Novi, however, their grandmother Kasandra later converted them into the Roman Catholic faith.