|List of Roman kings of the HRE|
|Nations that joined the HRE later: Poland | Prussia|
|Nations that left the HRE: Bohemia | Florence | Switzerland|
|Nations that became defunct|
Luxemburg was a duchy in the western part of the HRE.
Rise to power
When in 1309 king Otto IV of the HRE died, Heinrich VII of Luxemburg (same as OTL, and the last recognizable Roman king) became new king. He managed to be crowned as Holy Roman Emperor by the pope in 1312, becoming the first emperor since Friedrich II.
In 1335, Heinrich of Tyrol died without male heirs; Tyrol would fall to the house of Luxemburg, via his daughter who married into this house.
The dynasty also had another Roman king, Karl IV of Luxemburg 1347-58 (emperor since 1353). They also managed to acquire other lands for the dynasty, like Brabant, Limburg and Lorraine.
Due to several heirs, in 1415 Luxembourg and Tyrol were divided, forming a second line.
In 1464, great findings of silver were made in Tyrol, which made the Luxemburger dynasty second-richest in the HRE. 1468, Limburg was split off Luxemburg for Udo. In 1472, their candidate Heinrich VIII was elected Roman king. His rule was overshadowed: 1473, Tyrol was split into West and East Tyrol; and when he secularized and annexed the bistums of Augsburg and Trient for his lands, the HRE fell into a kind of Civil War. All the princes tried to annex the clerical lands, which lead to lots of confusion and little wars for said lands, which are generally subsumed as the Twenty-Year War. The most important of those wars are the Bavarian-Austrian War for Salzburg (1485-93) and the French-Dutch War (1486-91). For some time, there were three kings in the Empire, one of them Karl V of Luxemburg. He managed to acquired the core of the electorate of Trier, including the city itself, which made the archbishop the dynasty's tool. Via Tyrol he also acquired Augsburg, Bressano / Brixen and Trient. After the end of the war and deposing anti-king Otto of Brandenburg, he was accepted as Roman king.
1502, the line of East Tyrol inherited Luxemburg; 1548, Limburg was inherited by Luxemburg-Tyrol; 1567-83, Görz was split off from West Tyrol. And after Heinrich VII of West Tyrol was deposed for complete madness, all Luxemburger lands were united under Karl IX (VI in Tyrol).
Unfortunately, after his death, the succession was unclear. The Luxemburgian War of Succession (1660-64) broke out when France and its allies Venice, Bavaria, Switzerland and Nassau made claims for Luxemburgian territories, although they were highly doubtful. But with the absolutist François IV as French king, things like this didn't matter. Although Luxemburg had (most of) the HRE on its side, they were defeated. Vorarlberg became a Swiss canton, South Tyrol went to Venice, the rest of Tyrol to Bavaria; Nassau got a part of Luxemburg proper, the rest (including Lorraine) became French. The rightful heir, Karl X (VII in Tyrol) only received Brabant-Limburg. "The old sting in France's side", as François IV said, was now removed.
In the first French Republican War, Luxemburg was overrun by French troops and annexed afterwards. It stayed like this until 1827, when freshly united Germany took German-speaking Luxemburg back after the Rhenish War.