Portable corneal axis marker to adapt to smartphones for ophthalmic use, consisting of a base adaptable to smartphones, a body and an end to mark eye tissues, characterized by a base that adapts to the smartphone (1) that leaves the lens of the cleared chamber, a rigid body of cylindrical or conical shape (2) and an end to mark ocular tissues (3) that has two elements, internal and external, circular and concentric. The external element is fixed and has two fixed marks at 0 and 180 degrees (5) and an engraving that indicates the axes to be marked. The internal element is mobile and rotatable 360 degrees and has two opposite marks (4). The marks that come into contact with the eye tissue are blunt and curved following the anatomy of the cornea and eyeball. (Machine-translation by Google Translate, not legally binding)