The Cantacuzino or Cantacuzène family is a Romanian aristocratic family that gave several Princes of Wallachia and Moldavia, descending from a branch of the Byzantine Kantakouzenos family, specifically from the Byzantine EmperorJohn VI Kantakouzenos (reigned 1347–1354). After the Russo-Ottoman War of 1710–11 a branch of the family settled in Russia, receiving the princely (Knyaz, as opposed to Velikij Knyaz) status. In 1944 Prince Ștefan Cantacuzino settled in Sweden, where his descendants form part of the unintroduced nobility of the country.
Members of the family claim that the genealogical links between the Byzantine Greek and Romanian branches of the family have been extensively researched. The family first appears among the Phanariotes in the late 16th century, with Michael "Şeytanoğlu" Kantakouzenos, after a gap of over a century from the Fall of Constantinople. Whether the family is indeed linked to the Byzantine imperial house of Kantakouzenos is disputed, as it was usual among wealthy Greeks of the time to assume Byzantine surnames and claim descent from the famous noble houses of their Byzantine past. The eminent Byzantinist Steven Runciman considered the latter-day Kantakouzenoi "perhaps the only family whose claim to be in the direct line from Byzantine Emperors was authentic", but according to the historian Donald Nicol, "Patriotic Rumanian historians have indeed labored to show that ... of all the Byzantine imperial families that of the Kantakouzenos is the only one which can truthfully be said to have survived to this day; but the line of succession after the middle of the fifteenth century is, to say the least, uncertain."