Trakai Island Castle (Lithuanian: Trakų salos pilis) is an island castle located in Trakai, Lithuania on an island in Lake Galvė. The castle is sometimes referred to as "Little Marienburg".

According to the chronicle legend, after a successful hunt, Grand Duke of Lithuania Gediminas  found a great place near the town of Kernave and decided to erect a castle on it and move the capital here. In the second half of the 14th century, here in the Old Traki (Syaneyi Trakai), was standing stone castle. Rules to them in 1337-1382 son of Gediminas Kęstutis. Around 1350 in the castle was born Vytautas. In 1375, Kęstutis moved his capital from Old Traki to New Traki, which was protected by Lake Galvė. The construction of Trakai Island Castle was related to the expansion and strengthening of the Trakai Peninsula Castle. Castle in the Old Traki in 1391 was destroyed and never rebuilt. In 1405, a plot of land with the remains of the old castle was given to the Benedictine monks. The monastery stands on the old citadel.
The castle was damaged during an attack by the Teutonic Knights in 1377. After the assassination of Kęstutis, a power struggle between Jogaila and Vytautas the Great for the title of Grand Duke of Lithuania began. The castle was besieged by both sides and was severely damaged. Soon after the reconciliation between Jogaila and Vytautas, the second phase of construction started. This phase is regarded as the major development in the history of the castle. Apparently, during the truce with the Teutonic Order, the construction works were supervised by the Order's stonemason Radike.

 Trakai Island Castle was completed in 1409. It was the most powerful and the most majestic of all the Grand Duchy of Lithuania. It was one of the most impregnable fortresses in Eastern Europe: the castle was never captured by its enemies. Trakai Island Castle originally combined defensive and representational functions, ie, functions of the fortress and palace. He is an excellent example of Gothic architecture. Center of the architectural ensemble of the castle is a princely palace, surrounded by thick walls and fortifications which is under protection of defensive towers. The state rooms of the palace is decorated with stained glass windows and frescoes, the main subjects which were scenes from the life of the great princes. Dwellings connected by an internal wooden galleries. Between the bedroom and the prince of the treasury chamber was a secret passage that led to the courtyard. The castle was equipped with air heating: Hot air rises through the pipes and warmed the cold stone walls. About unprecedented wealth castle reflected in the fact that, as is clear from the Lithuanian chronicles, even seat in the castle were gold.