Orbital myositis is an inflammatory process that primarily involves the extraocular muscles and most commonly affects young adults in the third decade of life, with a female predilection. Clinical characteristics of orbital myositis include orbital and periorbital pain, ocular movement impairment, diplopia, proptosis, swollen eyelids, and conjunctival hyperemia. The most common presentation is acute and unilateral, which initially responds to systemic corticosteroid therapy. However, chronic and recurrent cases may involve both orbits. Many inflammatory, vascular, neoplastic, and infectious conditions that affect the extraocular muscles and other orbital tissue can mimic orbital myositis. The most important differential diagnoses include thyroid-related eye disease, other orbital inflammatory processes (unspecific idiopathic inflammation, vasculitis, and sarcoidosis), orbital cellulitis, and orbital tumors. In refractory, chronic, or recurrent cases, steroid-sparing agents, inmmunosuppressants, or radiation therapy may be indicated.