Graf Gustav Ernst von Stackelberg (Russian: ) (5 June 1766, Reval, Governorate of Estonia - 18 April 1850, Paris, France) was a Russian diplomat of Baltic-German descent, and was the son of Otto Magnus von Stackelberg.
As a Lieutenant in the Russian armed forces he fought in the Russo-Swedish War against King Gustav III of Sweden. After he left the army, he became a diplomat of the Russian court, initially as a chamber junker of Empress Catherine the Great.
After the defeat of France in the Napoleonic Wars, he worked as a diplomat and ambassador of Russia at the Congress of Vienna in 1814--1815, and was pivotal in the absorption of most of the Duchy of Warsaw into the Russian Empire as the Kingdom of Poland.
After a long career as a diplomat, he was awarded the Order of St. Andrew, and spent his retirement in Paris, where he died in 1850.