A window unit for an aircraft includes a wall module having a side wall laterally delimiting an aircraft cabin. The side wall has a window opening and the wall module has retaining portions. A window module has a window frame accommodating at least one windowpane and the window module has fastening portions. A fastening configuration fastens the window module on the side wall in a region of the window opening. The fastening configuration is formed by a respective fastening portion engaging with a respective retaining portion. The retaining portions and the fastening portions are movable into a plug-in position by a plug-in movement of the window module and are movable from the plug-in position into a securing position by a rotary movement of the window module. The wall module and the window module are interconnected by a form-locking connection in the securing position.