The Wachau (German pronunciation: [vaˈxaʊ̯] ^ⓘ) is an Austrian valley formed by the Danube River. It is one of the most prominent tourist destinations of Lower Austria, located between the towns of Melk and Krems that attracts epicureans for its high-quality wines. It is 36 kilometres (22 mi) in length and has been settled since prehistoric times. Among the tourist attractions is Dürnstein Castle, where King Richard I of England was held captive by Leopold V, Duke of Austria. The architectural elegance of its monasteries (Melk Abbey and Göttweig Abbey), castles and ruins combined with the urban architecture of its towns and villages, and the cultivation of vines as an important agricultural produce are the dominant features of the valley.

The Wachau was inscribed as "Wachau Cultural Landscape" in the UNESCO List of World Heritage Sites in recognition of its architectural and agricultural history, in December 2000.

Even before the Neolithic period brought in changes in the natural environment of the valley, Palaeolithic records of the valley have been identified in the form of "figurines" in Galgenberg and Willendorf, stated to be 32,000 years and 26,000 years old, respectively, that testify to human occupation in the valley. It has been inferred that Krems and Melk were well settled establishments in the early Neolithic period between 4500 BCE and 1800 BCE. Wachau Valley's ancient history in the Neolithic period started with deforestation by the people of the land for cultivation and settlement.

In 15 BCE, the Celtic kingdom of Noricum became part of the Roman Empire. Since then, the Empire's boundaries were made up along the Danube. The fortifications of the limes were built along its southern banks, especially Castrum Favianis (what is now Mautern an der Donau) at the downstream end of the valley and some burgi (i.e., small watchtower-like fortresses) in the area of Rossatz-Arnsdorf municipality, the remains of which can still be seen today, most notably in Bacharnsdorf. Roman rule on the southern banks of the Danube came to an end when King Odoaker ordered the evacuation of the Latin speaking population in 488 CE.

The name "wachu", as such, was recorded as "locus Wahowa" in 853 AD and the name of "Krems" was recorded as Urbs Chremisa in 995 CE, marking it as the oldest Austrian town.

The Babenberg Margraves, with Leopold I as their first king, ruled in Wachau from 976 CE. The 11th century marked an Austrian dukedom of Babenberg under Henry II, in 1156. After the dissipation of this line of rule, Duke Albert V (King Albert II) came to power in 1404. Between 1150 and 1839 CE, the four towns of St Michael, Wösendorf, Joching, and Weissenkirchen functioned independently. However, they formed a single entity as Wachau or Tal Wachau only in 1972. In the 12th century, the King of England, Richard the Lionhearted, was imprisoned at the Kuenringerburg castle above the Dürnstein town because he insulted the Babenberg Duke, Leopold V by showing disrespect to the Austrian flag. Even though he was travelling in Austria returning from the Holy Lands in disguise, he was identified in an inn in Erdberg, now a suburb of Vienna. He was finally released after paying a kingly ransom of 35,000 kg of silver. According to myth, the king's freedom was facilitated due to the efforts of his French aide Blondel. It is said that this silver booty was used to build Wiener Neustadt.

Substantial changes in the landscape were witnessed during the medieval period from the 9th century with the establishment of the Bavarian and Salzburg monasteries. During this process of development, economic needs necessitated the creation of vine terraces to manufacture and market wine. In the 17th century, the area brought under vineyards varied widely depending on the climate and also the marketability of its wine. Viticulture on the hill slopes was practiced from the 18th century but adjustments in acreage brought under viticulture and pasture, and viticulture and horticulture (fruits) became necessary to meet the economic conditions in the region. Concurrent with this, the country side also started developing and this closely affected the agricultural practices in the region. Green Veltliner and Riesling grapes are still grown on steep terraces along the Danube River in the Wachau Valley.

Between 1150 and 1839, the four towns of St. Michael, Wösendorf, Joching and Weissenkirchen functioned independently. However, they formed a single entity as Wachau or Tal Wachau only in 1972. Wachau also had its fair share of invasions. The Hungarians invaded in the 15th century, and Matthias Corvinus occupied Krems and Stein in 1477. Church Reformists' activities also made an impact between 1530 and 1620, with the Protestants finally getting subdued by the Göttweig Abbot Georg II Falb in 1612–1631; eleven Austrian Benedictine abbeys had lent full support in this victory. This had a profound impact on the religious culture of the valley with many churches, chapels and other monuments being built in the valley. The history of town development in the valley dates back to the 11th and 12th centuries. This development was of a homogeneous character with wooden buildings constructed for housing in irregularly shaped streets. However, stone as building material was introduced in the 15th and 16th centuries to replace the old wooden structures by the peasants and the burghers. Since 1950, the residential complexes have appeared in the upper periphery of the valley.