The Wawel Royal Castle (Polish pronunciation: [ˈvavɛl] ^ⓘ; Zamek Królewski na Wawelu) and the Wawel Hill on which it sits constitute the most historically and culturally significant site in Poland. A fortified residency on the Vistula River in Kraków, it was established on the orders of King Casimir III the Great and enlarged over the centuries into a number of structures around a Polish Renaissance courtyard. It represents nearly all European architectural styles of the Medieval, Renaissance and Baroque periods.

The castle is part of a fortified architectural complex erected atop a limestone outcrop on the left bank of the Vistula River, at an altitude of 228 metres (748 ft) above sea level. The complex consists of numerous buildings of great historical and national importance, including the Wawel Cathedral where Polish monarchs were crowned and buried. Some of Wawel's oldest stone buildings can be traced back to 970 CE, in addition to the earliest examples of Romanesque and Gothic architecture in Poland. The current castle was built in the 14th century, and expanded over the next hundreds of years. In 1978, Wawel was declared the first World Heritage Site as part of the Historic Centre of Kraków.

For centuries the residence of the kings of Poland and the symbol of Polish statehood, Wawel Castle is now one of the country's premier art museums. Established in 1930, the museum encompasses ten curatorial departments responsible for collections of paintings, including an important collection of Italian Renaissance paintings, prints, sculpture, textiles, among them the Sigismund II Augustus tapestry collection, goldsmith's work, arms and armor, ceramics, Meissen porcelain, and period furniture. The museum's holdings in oriental art include the largest collection of Ottoman tents in Europe. With seven specialized conservation studios, the museum is also an important center for the conservation of works of art. With over 3.1 million visitors in 2024, Wawel Castle is the most visited art museum in Poland and the 17th most visited art museum in the world.

The history of Wawel is deeply intertwined with the history of the Polish lands and Polish royal dynasties already in the Middle Ages. The political and dynastic tensions that led to the ascendance of Kraków as the royal seat are sophisticated, but for most of the Middle Ages and the Renaissance Wawel was the seat of the national government and the Diet (assembly). As the Polish–Lithuanian Commonwealth formed and grew, Wawel became the seat of one of Europe's largest and most important states. This status was only lost when the capital was moved to Warsaw in 1596 (designated officially in 1793).

From the late 18th century, when Poland lost its independence during the period of foreign partitions, Wawel became a symbol of endurance and was the setting for demonstrations and gatherings of Krakowians protesting against the continuing foreign occupation by the Austrian, Prussian, and the Russian Empires. Thus, the significance of the Wawel Hill comes in part from its combination of political and religious significance. The Cathedral holds the relics of St. Stanislaus and stands directly adjacent to the Royal Castle. The Hill has a long history of religious functions; some of the oldest extant architectural remains are those of the Rotunda of the Virgin Mary.

The hill which takes the form of a horst originated in the Miocene epoch (23–25 million years ago) and consists of Jurassic limestone dating back to the Oxfordian age (155–161 million years ago). This limestone is strongly karsted and abounds in caves (e.g. the Dragon's Den—Smocza Jama). This possibly explains why the hill was originally called "wąwel", meaning ravine in Polish. This ravine once divided the hill. An alternative theory is that the word means 'protrusion from the marshes' which surrounded the hill. However, the most recent theory is that "Wawel" is a regular continuation of the name Babel in the Greek language (the consonant [B] followed by [V]/[W]).

The Wawel Hill has archaeological remains indicating settlement from the 4th century. Archaeological studies suggest that the earliest settlement dates back to the Middle Paleolithic era, c. 100,000 years BC and owed its rapid development to its location being the crossing of a number of key trading routes. Wawel is believed to be one of the strongholds of the Vistulan tribe which formed a nation at the turn of the 8th and 9th century AD. Its legendary rulers Krakus and Princess Wanda, who are said to have lived in the 7th and 8th centuries, are mentioned by the 13th-century chronicler Wincenty Kadłubek. In the 10th century, the Vistulans' lands and Kraków became part of the emerging state of Poland.

In the year 1000, the Kraków diocese was established followed by the construction of a Cathedral – the seat of the bishop. However, as a result of an ongoing conflict with the Holy Roman Empire, construction did not begin until the signing of the Peace of Bautzen, in 1018. Only minor fragments remain of the original cathedral (which is sometimes called 'Chrobrowska' after Bolesław I the Brave) and despite extensive archaeological research, it has proved impossible to reconstruct its exterior. Until the 1980s, relicts of St Gereon's Church were identified with the first cathedral but this theory, advanced by Adolf Szyszko-Bohusz, has been disproved by more recent research. There are also inconsistencies in the dating of the destruction of the original cathedral. Some sources place this at the time of the invasion of Bretislaus I of Bohemia in the 1040s, while others date the destruction to a fire in the 1080s.