An optical system with adjustable eye relief includes a relay lens assembly. The relay lens assembly is defined by a collimating lens and a focusing lens. The optical system includes an aperture stop. The aperture stop is configured to shift axially along an optical axis between the collimating lens and the focusing lens. The optical system also includes an afocal lens assembly. The afocal lens assembly is defined by the focusing lens and an eyepiece. Additionally, an axial shift of the aperture stop along the optical axis between the collimating lens and the focusing lens changes an eye relief of the eyepiece based on a transverse magnification of the afocal lens assembly.