Royal house in the context of "Emperor Akihito"

The House of Savoy (Italian: Casa Savoia, French: Maison de Savoie) is a royal house (formally a dynasty) of Franco-Italian origin that was established in 1003 in the historical region of Savoy, which was originally part of the Kingdom of Burgundy and now lies mostly within southeastern France. Through gradual expansions, the family grew in power, first ruling the County of Savoy, a small Alpine county northwest of Italy, and later gaining absolute rule of the Kingdom of Sicily. During the years 1713 to 1720, they were handed the Kingdom of Sardinia and would exercise direct rule from then onward as Piedmont–Sardinia, which was the legal predecessor state of the Kingdom of Italy and the Italian Empire, which in turn are the predecessors of the present-day Italian Republic.

From rule of a region on the French–Italian border, by the time of the abolition of monarchy in Italy, the dynasty's realm grew to include nearly all of the Italian peninsula. Through its junior branch of Savoy-Carignano, the House of Savoy led the Italian unification in 1861, and ruled the Kingdom of Italy until 1946. They also briefly ruled the Kingdom of Spain during the 19th century. The Savoyard kings of Italy were Victor Emmanuel II, Umberto I, Victor Emmanuel III, and Umberto II. Umberto II reigned for only a few weeks, as the last king of Italy, before being deposed following the 1946 Italian institutional referendum, after which the Italian Republic was proclaimed.

The House of Lusignan (/ˈluːzɪn.jɒn/ LOO-zin-yon; French: [lyziɲɑ̃]) was a royal house of French origin, which at various times ruled several principalities in Europe and the Levant, including the kingdoms of Jerusalem, Cyprus, and Armenia, from the 12th through the 15th centuries during the Middle Ages. It also had great influence in England and France.

The family originated in Lusignan, in Poitou, western France, in the early 10th century. By the end of the 11th century, the family had risen to become the most prominent petty lords in the region from their castle at Lusignan. In the late 12th century, through marriages and inheritance, a cadet branch of the family came to control the kingdoms of Jerusalem and Cyprus. In the early 13th century, the main branch succeeded to the Counties of La Marche and Angoulême.

The House of Windsor is the current royal house of the United Kingdom and other Commonwealth realms. The house's name was inspired by the historic Windsor Castle estate. The house was founded on 17 July 1917, when King George V changed the name of the royal house from the German Saxe-Coburg and Gotha to the English Windsor due to anti-German sentiment during the First World War. There have been five British monarchs of the House of Windsor: George V, Edward VIII, George VI, Elizabeth II, and Charles III. The children and male-line descendants of Queen Elizabeth II and Prince Philip, Duke of Edinburgh, also genealogically belong to the House of Oldenburg since Philip was by birth a member of the Glücksburg branch of that house.

The monarch is head of state of fifteen sovereign states. These are the United Kingdom, Antigua and Barbuda, Australia, The Bahamas, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Solomon Islands, and Tuvalu. As well as these separate monarchies, there are also three Crown Dependencies, fourteen British Overseas Territories, two associated states of New Zealand, and one territory.

The Capetian dynasty (/kəˈpiːʃən/ kə-PEE-shən; French: Capétiens/ka.pe.sjɛ̃/), also known as the House of France (French: La Maison de France), is a dynasty of Frankish origin, and a branch of the Robertians agnatically, and the Carolingians through female lines. It is among the largest and oldest royal houses in Europe and the world, and consists of Hugh Capet, the founder of the dynasty, and his male-line descendants, who ruled in France without interruption from 987 to 1792, and again from 1814 to 1848. The senior line from the House of Capet ruled in France from the election of Hugh Capet in 987 until the death of Charles IV in 1328. That line was succeeded by cadet branches, first the House of Valois, and succeeding them the House of Bourbon, which ruled until the French Revolution abolished the monarchy in 1792 and tried and executed King Louis XVI in 1793. The Bourbons were restored in 1814 in the aftermath of Napoleon's defeat, but had to vacate the throne again in 1830 in favor of the last Capetian monarch of France, Louis Philippe I, who belonged to the House of Orléans, a cadet branch of the Bourbons. Cadet branches of the Capetian House of Bourbon are still reigning over Spain and Luxembourg.

The dynasty had a crucial role in the formation of the French state. From a power base initially confined to their own demesne, the Île-de-France, the Capetian kings slowly but steadily increased their power and influence until it grew to cover the entirety of their realm. For a detailed narration on the growth of French royal power, see Crown lands of France. Members of the dynasty were traditionally Catholic, and the early Capetians had an alliance with the Church. The French were also the most active participants in the Crusades, culminating in a series of five Crusader kings – Louis VII, Philip Augustus, Louis VIII, Louis IX, and Philip III. The Capetian alliance with the papacy suffered a severe blow after the disaster of the Aragonese Crusade. Philip III's son and successor, Philip IV, arrested Pope Boniface VIII and brought the papacy under French control. The later Valois, starting with Francis I, ignored religious differences and allied with the Ottoman sultan to counter the growing power of the Holy Roman Empire. Henry IV was a Protestant at the time of his accession, but realized the necessity of conversion after four years of religious warfare.

The House of Saxe-Coburg and Gotha (/ˌsæks ˈkoʊbərɡ ... ˈɡɒθə, - ˈɡɒtə/ SAKS KOH-bərg ... GOT(H)-ə; German: Haus Sachsen-Coburg und Gotha), known until 1826 as the House of Saxe-Coburg-Saalfeld (Haus Sachsen-Coburg-Saalfeld), is a European royal house of German origin. It takes its name from its oldest domain, the Ernestine duchy of Saxe-Coburg and Gotha, and its members later sat on the thrones of Belgium, Bulgaria, Portugal, and the United Kingdom and its dominions.

Founded in 1826 by Ernest Anton, the sixth duke of Saxe-Coburg-Saalfeld, it is a cadet branch of the Saxon House of Wettin. One agnatic branch currently reigns in Belgium—the descendants of Leopold I—and another reigned in the United Kingdom until the death of Elizabeth II—the descendants of Albert, Prince Consort.

The House of Plantagenet (/plænˈtædʒɪnɪt/ plan-TAJ-in-it) was a royal house which originated in the French county of Anjou. The name Plantagenet is used by modern historians to identify four distinct royal houses: the Angevins, who were also counts of Anjou; the main line of the Plantagenets following the loss of Anjou; and the Houses of Lancaster and York, two of the Plantagenets' cadet branches. The family held the English throne from 1154, with the accession of Henry II, until 1485, when Richard III died in battle.

England was transformed under the Plantagenets, although only partly intentionally. The Plantagenet kings were often forced to negotiate compromises such as Magna Carta, which constrained royal power in return for financial and military support. The king was no longer just the most powerful man in the nation, holding the prerogative of judgement, feudal tribute and warfare, but had defined duties to the realm, underpinned by a sophisticated justice system. By the end of the reign of Edward III, the Plantagenets developed a new identity including adopting the language of the ordinary people—Middle English—as the language of governance. This is one of the reasons that the Oxford Dictionary of National Biography considers Edward III as culturally the first English Plantagenet ruler.