Ambras Castle (German: Schloss Ambras) is a Renaissance castle and palace located in the hills above Innsbruck, Austria. Ambras Castle is 632 metres (2,073 ft) above sea level. Considered one of the most popular tourist attractions of Tyrol, Ambras Castle was built in the 16th century on the spot of an earlier 10th-century castle, which became the seat of power for the Counts of Andechs. The cultural and historical importance of the castle is closely connected with Archduke Ferdinand II (1529–1595) and served as his family's residence from 1567 to 1595. Ferdinand was one of history's most prominent collectors of art. The princely sovereign of Tyrol, son of Emperor Ferdinand I, ordered that the medieval fortress at Ambras be turned into a Renaissance castle as a gift for his wife Philippine Welser. The cultured humanist from the House of Habsburg accommodated his world-famous collections in a museum: the collections, still in the Lower Castle built specifically for that museum's purpose, make Ambras Castle one of the oldest museums in the world.

The Lower Castle contains armouries that feature masterpieces of the European armourers' art from the time of Emperor Maximilian I to Emperor Leopold I. As the only Renaissance Kunstkammer of its kind to have been preserved at its original location, the Chamber of Art and Curiosities (Kunst- und Wunderkammer) is an unrivalled cultural monument.

Above the Lower Castle is the famous Spanish Hall (Spanischer Saal), a notable example of German Renaissance architecture, which contains an intricate wood-inlay ceiling and walls adorned with 27 full-length portraits of the rulers of Tyrol. The Upper Castle contains the extensive Habsburg Portrait gallery (Habsburger Porträtgalerie) featuring paintings of numerous members of the House of Austria and other leading ruling European dynasties, including, as a remarkable feature, many portraits of princely children.

Long before Innsbruck became a city, references to an Amras or Omras appeared in documents dating from the 10th century. This early fortification in what was then the southwest corner of Bavaria was the seat of power of the Counts of Andechs, who became Margraves of Istria and later Dukes of the short-lived Imperial State of Merania from 1180 to 1248. This original fortification was destroyed in 1133 and no traces of it remain, although some of the material from the original structure was later used in the modern building. In 1248, the castle ruins and property passed by inheritance from the Counts of Andechs to Albert IV, Count of Tyrol.

The modern Ambras Castle was built by Archduke Ferdinand II (1529–1595), the second son of Emperor Ferdinand I. When he was made provincial sovereign of Tyrol in 1564, Ferdinand II ordered two Italian architects to turn the existing medieval fortress into a Renaissance castle for his untitled wife Philippine Welser (1527–1580), whom he had married in secret. Ferdinand II prepared his family's residence in the Upper Castle, beneath which he constructed one of the most artistically important halls of the late Renaissance—known as the "Spanish Hall" since the nineteenth century. In 1567, Ferdinand II made his entry into Innsbruck, prior to that, he was appointed administrating governor of the Kingdom of Bohemia, taking up residence in Prague in 1547. In 1589, he added an additional building, the Heldenrüstkammer, west of the Lower Castle for the purpose of housing his collection of "Heroes", the very first systematic presentation of objects in the history of museums. Ambras Castle was used as the residence of Philippine as well as a place for Ferdinand II to house his collection of weapons, suits of armour, portraits, natural objects, as well as rarities and precious objects. Today, the art history museum Schloss Ambras Innsbruck Archived 2019-03-29 at the Wayback Machine is part of the Kunsthistorisches Museum Vienna.

Philippine became a popular and beloved figure through her charity and willingness to help others, particularly the common people of Tyrol. Even the nobility brought their petitions to the former commoner. As signs of affection, people addressed their written petitions to "Merciful Miss" or "serene Princess Mrs. Philippine of Austria". After Ferdinand's death in 1595, the second son of Ferdinand and Philippine, Charles, Margrave of Burgau, inherited Ambras Castle. With little interest in preserving the castle or its collections, they fell into a state of dilapidation and Charles sold them in 1606 to Emperor Rudolf II. The emperor residing in Prague left his uncle's collection nearly in its entirety at Ambras Castle, as he himself was one of the most important Habsburg collectors.

In the following years, Ambras Castle no longer had the status of an official residence and was seldom lived in. Inadequate preservation measures led to the loss of valuable books, manuscripts, and hand sketches, and soon the palace fell largely into disrepair. In the seventeenth century, Emperor Leopold I (1640–1705) had some of the most valuable holdings of the Ambras collections—mostly books and manuscripts—moved to Vienna, where they can still be seen at the Austrian National Library. In 1805, the remaining Ambras collections were threatened by the defeat of Austria by the French Empire. Fortunately, after he recognized the private-law character of the Ambras collection, Napoleon (1769–1821) had it brought to safety in Vienna.

In 1855, Archduke Karl Ludwig, then governor of Tyrol, had the palace remodeled to use as a summer residence. Significant changes were made during this time to the palace and the surrounding park. The Outer Bailey (Vorschloss) was constructed with an ivy-clad entrance ramp for carriages. The park was redesigned as an English garden. Following Archduke Karl Ludwig's renouncement of his succession rights in 1889, the palace fell once again into ruinous condition. In 1880, it was converted into a museum and subsequently renovated.