In spite of their fondamental geopolitical differences and their contrasting trajectories through the history, modern-day Romania and Luxembourg have always enjoyed a unique relationship, which started in the 12th century, when a number of Siebenbürger Sachsen could migrate eastwards (in Transylvania). A second migratory movement occurs in the 18th century when inhabitants of the then Duchy of Luxembourg set off towards the Danubian plains (the Banat of Timisoara), establishing themselves as settlers on this land previously conquered by the Habsburgs from the Turks and today part of Romania. Bilateral diplomatic relations between Romania and Luxembourg were first established on 8 December 1920, and in 1966 their respective diplomatic representations were elevated to the rank of embassy. After the fall of the communist regime, the democratic government of Romania appointed, in 1990, its first resident ambassador in Luxembourg. During its gradual integration into the Euro-Atlantic structures (EU, NATO), Romania and Luxembourg increase their synergies in a bi- and multilateral international framework. Moreover, on 5 April 2005, Romania (and Bulgaria) signed the EU accession treaty in Luxembourg, under the Luxembourg Presidency of the Council of the European Union. Taking into account these elements, and also the fact that Romania and Luxembourg (both, independent and sovereign nation-states) are subjects of the international relations and diplomacy process, this lecture aims to present a insightful foray into a long-centuries common history, by highlighting moments, events and key-figures on both-sides, by means of several undisclosed and unpublished archival documents provided courtesy of the Diplomatic Archives of Romania. (A brief presentation of definitions, concepts and notions specific to the international relations and diplomacy field will ensure a better understanding of the subject).