A two-dimensional/three-dimensional (2D/3D) switchable autostereoscopic display apparatus is provided, including a display panel and a lenticular unit with a two-dimensional mode and a three-dimensional mode. In the two-dimensional mode, the lenticular unit transmits a single image, and in the three-dimensional mode, the lenticular unit separates an image from the display panel into a right-eye image and a left-eye image. The lenticular unit includes first and second lenticular lens sheets, a half-wave plate interposed between the first and second lenticular lens sheets, which rotates a polarization of incident light by 90 degrees, and first and second electro-optical mediums disposed between the first lenticular lens sheet and the half-wave plate and between the second lenticular lens sheet and the half-wave plate, respectively. First and second electro-optical media have refractive indices with respect to extraordinary rays that vary based on electric fields applied to the first and second electro-optical media.