Nijo Castle is a flatland castle in Kyoto, Japan. Built in 1603, this cyprus-wood castle with extensive gardens was a home for the shogun Ieyasu.

Nij0 Castle has two concentric rings of fortifications, each consisting of a wall and a wide moat. The outer wall has three gates while the inner wall has two. In the southwest corner of the inner wall, there are foundations of a five-story keep, destroyed by a fire in 1750. The inner walls surround the Inner Ward, which contain Honmaru ("Inner Ward") Palace with its garden. Ninomaru ("Second Ward") Palace, the kitchens, guard house and several gardens are located in the Outer Ward, between the two main rings of fortifications.

The surface area of the castle is 275,000 square metres of which 8,000 square metres  is occupied by buildings. It is one of the seventeen Historic Monuments of Ancient Kyoto which have been designated by UNESCO as a World Heritage Site.

In 1939, the palace was donated to the city of Kyoto and opened to the public the following year. In the 21st century, typhoons have periodically caused sections of plaster to peel off the walls after exposure to rain and wind.