A 4-year-old Belgian Warmblood mare suffering from pelvic flexure impaction was diagnosed with ateratoma of the left ovary. The enlarged ovary was identified several days after treatment of the impaction.Surgical removal of the affected ovary was performed and histopathological examination confirmed thepresence of a teratoma. The features of another ovarian teratoma, which was an accidental finding at slaughter,are also described.