Disclosed herein is a liquid crystal display device having a thin thickness and a reduced size of a bezel. According to an exemplary embodiment, the liquid crystal display device includes: a liquid crystal display panel including a display area and a non-display area enclosing the display area; a light guide plate disposed under the liquid crystal display panel and having a polygonal plane shape including a first side, a second side, a third side, and a fourth side; and a light source adjacent to the first side of the light guide plate, wherein at least one of the second side, the third side, and the fourth side of the light guide plate overlaps the display area.