The lips are highly visible structures on the face, providing oral competence and expressing emotion. The reconstruction of large full-thickness defects of the lips is a formidable challenge for the plastic surgeon. The most challenging defect of the lower lip is full thickness, larger than two thirds. Such an extensive defect requires either staged reconstruction or a flap of distant tissue. We consider that the gracilis muscle, due to its anatomic and functional features, is the ideal flap for reconstruction of the lips. A functioning gracilis matches all the requisites and allows normal movements that are uniform to all of the lip. The new commissure is symmetric and moves simultaneously with the residual commissure due to innervation by the facial nerve. Our indications to use the functioning gracilis muscle flap in lip reconstruction are as follows: resection of the lower lip larger than one quarter of the lip length in a patient younger than 60 years; resection larger than one third of the lip in all patients. When performing a free gracilis flap for lip reconstruction, we consider that, if possible, a facial artery musculomucosal flap and sensitive neurotization should be included to restore sensation of the reconstructed lip.