Alexandru Cantacuzino-Deleanu or Alexandros Kantakouzinos (Greek: Αλέξανδρος Καντακουζηνός: 1787 in Iași, Moldavia – 1841 in Athens, Greece) was a Phanariote Romanian-Greek magnate and politician.
Alexandros Kantakouzinos was born in Iași, in the principality of Moldavia, as a younger son of the boyar Matei Cantacuzino-Deleanu (c. 1750 – c. 1817), justiciar of Moldavia and state councillor of the Russian Empire, and his wife princess Ralou ('Rhalouka', 'Ralitza') Callimachi (1763–1837). Matei Cantacuzino belonged to the Phanariote Greek Cantacuzino family, which had long settled in the Danubian Principalities.
Alexandros Kantakouzinos was born during the Russo-Turkish War of 1787–1792, during which Russia occupied parts of the Danubian Principalities for several years. In 1791, Matei Cantacuzino entered Russian service, and the family followed the departing Russian troops to the Russian Empire. Alexandros Kantakouzinos served as a chamberlain to the Russian tsar. As young man, he married the Ukrainian noblewoman Elisabeta Darahan, a grand-niece of the last Hetman of Ukraine, the last sovereign lord of the Zaporozhian Cossacks. The matrimony made Alexandros a married-in-member of the influential Rozumovski clan – his wife's cousins, who at this time held such eminent positions as Ambassador to the Austrian court in Vienna, and Minister of Education in St. Petersburg. His brother, Grigore Cantacuzino-Deleanu served in the Imperial Russian Army and rose to the rank of colonel, before being killed in the Battle of Borodino in 1812 against Napoleon's invasion of Russia.