The historical palace of the Hungarian kings in Budapest, Hungary, is known as Buda Castle or Buda Palace. It was formerly known as both the Royal Castle and the Royal Palace.

At the southern tip of the hill where it is now, close to the Castle District, which is renowned for its mediaeval, Baroque, and 19th-century homes and public structures, the castle was constructed in the late Gothic style during the 14th century.

The castle was extensively rebuilt in the late Baroque style in the middle of the 18th century (1748–1769) as a representation of Habsburg control over Hungary after the Ottoman Empire was defeated.

The building's current addition, however, dates from the second half of the 19th century, when Miklós Ybl and Alajos Hauszmann doubled its surface area in an ostentatious neo-baroque design. The resulting castle, which wasn't finished until 1904, ended up being one of Europe's largest and most opulent royal homes.

Due to its commanding position over the city, the Royal Castle sustained significant damage during the Budapest Siege near the end of World War II. The structure was being rebuilt in a strict neoclassical style by the new communist Hungarian administration, who took advantage of its semi-ruinous state. In place of the flamboyant fin-de-siècle decorations and the various allusions to the Habsburg monarchy, a more neutral, ahistorical design was used. The formerly regal chambers were replaced by vast display halls inside. The Hungarian National Gallery and the Budapest History Museum are just two examples of the numerous institutions that have been built in the mediaeval fortress. The nineteenth-century gardens on the hill's slope also vanished to make room for the reconstruction of the mediaeval defences.

Budapest's World Heritage Site, which was designated a World Heritage Site in 1987, includes Buda Castle.

On the present-day site of Budapest, the Roman city of Aquincum previously stood. It was surrounded by a large number of towns that quickly vanished once the Huns, Avars, and subsequently Hungarians arrived in 985. Although the exact locations are unknown, Buda's town was founded along the Danube near to Kelenföld Hill after the Hungarians entered the Carpathian Basin.

Esztergom, the birthplace of the first Hungarian king St. Stephen I of Hungary, was the city where the court was situated when the Hungarians began to become Christians about a century later, in the year 1000. However, following his passing, it was transferred to Székesfehérvár, a city that had been established in 972 by the Great Prince Géza of Hungary, the ancestor of St. Stephen I.

Following the Tatar invasion in 1241, King Bela IV of Hungary started the process of rebuilding all the fortifications, fortifying them with stone walls, and ordered the construction of nearly a hundred additional castles in the middle of the 13th century. As a result, he gave the order to build a fortress at Buda in 1244, not far from the current location, which quickly saw the influx of people. Since then, subsequent Hungarian kings have spent a lot of time in this new citadel without cutting off communication with Székesfehérvár. Even Andrew III of Hungary signed documents and maintained a permanent residence at Buda, where he passed down in 1301. As a result, Buda's strategic, economic, and political importance increased to the point where, in addition to Esztergom and Székesfehérvár, all potential heirs to the throne attempted to live there during the interregnum period of over seven years following the death of Andrew III.

The crowning of pretender Charles Robert of Anjou-Sicily took place in Széfeshérvár on August 27, 1310, and once he won, Buda became the formal residence of the Hungarian king and his court.

Buda Castle had continuous renovations over the ensuing decades under the direction of Charles Robert and, after his death, Ludwig I of Hungary. The Hungarian monarchy and all of its subordinate nations from the Balkans to the Carpathian Basin were ruled from here. Royal assemblies, jousts and tournaments, diplomatic meetings, and royal assemblies were all conducted here. Buda Castle steadily became more opulent, and during the reign of Sigismund of Luxembourg in the 14th and 15th centuries, the most substantial modifications were made using materials imported from Austria and Bohemia.

Buda attained its splendour in the 15th century, during the Renaissance era, when the Hungarian King Matthias Corvinus modified Sigismund of Luxembourg's design and added Renaissance embellishments to the exterior façade and interior walls. The Matthias Church was nearly completely refurbished while keeping many of its Gothic elements, making it stand out among more modern buildings. The castle, which became one of the most significant gathering places in Central and Eastern Europe, was inhabited by singers, writers, painters, astronomers, and humanists, as was customary in Renaissance courts.

It retained its significance after Matthias' death until 1526, when Hungary's history was altered by the Ottomans' victory against his army at the Battle of Mohács and the death of King Ludwig II of Hungary in combat. The German prince Ferdinand I of Habsburg and the Transylvanian voivode, both of whom were anointed kings of Hungary, battled it out for the Hungarian throne.

They later made a secret agreement in which John Szapolyai was to inherit Ferdinand. Sultan Suleiman the Magnificent used this agreement as justification to invade Hungary. Buda Castle was taken by the Ottoman army in 1541 after they routed Hungarian resistance. The Turks continued to hold the castle for about 160 years during their occupation of central Hungary, retaining the Principality of Transylvania as a vassal state.

After the sultan's failed effort to capture Vienna in 1683, Leopold I of Habsburg, the Hungarian king and Germanic emperor, dispatched Germanic soldiers to Hungary in 1686, where they were successful in removing the Turks from Buda Castle. Even though the Hungarian kingdom was united and Buda remained its capital, the monarch's court continued to be held in Vienna because the Habsburg emperors who held the Hungarian crown resided there.

Several walls, buildings, and towers were blasted to rubble by cannonballs during the Liberation of Buda, thus after the stronghold and the city were retaken from the Turks, they underwent considerable restoration. A royal house at Buda Castle was built by Maria Theresa I of Austria, Franz Joseph I, and other members of the House of Habsburg, who made significant improvements throughout history. Miklós Ybl and Alajos Hauszmann both planned and carried out renovations and restorations in the 19th century.

The Axis German soldiers' last position in the Hungarian monarchy during the siege of Budapest in 1944–1945 was Buda Castle. The palace was reduced to ruins once more by intense gunfights and artillery fire. The Soviet siege was finally broken by the defenders as a last resort, although they completely failed and abandoned 90% of their forces in the neighbouring streets of Buda. Presumably aware of their plans, the Russians moved quickly with heavy weapons toward potential escape routes. Many historians compare this to the Russian march on the Don in 1943 as one of the greatest military disasters in Hungarian history.

One of the simplest routes is to take the metró 2/red or tram 4/6 to Széll Kálmán plaza, then bus 16 from Várfok street. The "várbusz," or "the castle bus" in Hungarian, will carry you right to the top of the palace complex.