The House of Frankopan (Croatian: Frankopani, Frankapani, Italian: Frangipani, Hungarian: Frangepán, Latin: Frangepanus, Francopanus) was a Croatian noble family, whose members were among the great landowner magnates and high officers of the Kingdom of Croatia in union with Hungary.

However Croatian Encyclopedia,[4] Italian Encyclopedia[6] and German Biographical Lexicon of the History of Southeastern Europe[7] by the Leibniz Institute for East and Southeast European Studies highly question the bloodline connection between the two families and remind of the common fashion of medieval noble families in Europe to try and connect themselves to ancient Roman nobility.

Along with the members of the Zrinski family the Frankopan ranked high in terms of importance by virtue of power, wealth, fame, glory and role in Croatian and Hungarian history.

The first known member of Croatian lineage of the Frankopan family was Dujam I Krčki (Doymus Veglensis in Latin sources that also attribute the title of comes to him[8][9]), lord of Krk who received permission by Domenico Michieli, Doge of Venice from 1118 to 1130, to rule the island of Krk as vassal of the Republic of Venice.

[4][6][2] In 1221, the brothers Henry and Servidon Frankopan received the islands of Brač, Hvar, Korčula and Lastovo as a gift from King Andrew II of Hungary for their services.

[1][11] In 1240–1241 the Mongol Empire advanced from Poland toward Hungary whose King, Béla IV resisted bravely but finally had to seek refuge in Dalmatia.

[12] In 1246 there was another war, between Frederick II, Duke of Austria and Béla, who, with the assistance of the Frankopan, won a victory.

[19] In the late 1990s, Louis's cousin Mirko Jamnicki-Dojmi di Delupis wrote an open letter where he denounced claims over Frankopan, Šubić and Zrinski names by his family and presented the family tree of Dojmi di Delupis containing 129 names from the year 1200 onwards.

[22] Louis's descendants include Lady Nicholas Windsor,[23] and historian Peter Frankopan who also claimed that they always had the same name.

Other castles or property of the Frankopans could be found in Ribnik, Bosiljevo, Novi Vinodolski, Drivenik, Ogulin, Slunj, Ozalj, Cetingrad, Trsat, and other surrounding towns.