Abstract: The portable monocular comprises an elongate body in two parts (2,3) at one end of which is fixed an eyepiece (1). At its other end the elongate body encloses two biconvex lenses (4,4') of equal power arranged in grooves (5,5'). The distance (A) between the first lens (4) and the second lens (4') is equal to half the focal distance of the first lens (4) and is less than or equal to a diameter of this first lens. The relationship between the distance A and the distance B separating the second biconvex lens (4') from the eyepiece (1) is such that 3A.ltoreq.B.ltoreq.4A.