Although many algorithms exist to classify oral cavity defects, they are limited by either considering a single subsite or failing to provide a concise reconstructive algorithm for the breadth of defects. Based upon our experience as a tertiary referral center, a unifying algorithm is presented that guides free flap selection in this heterogenous population. Methods: All intraoral defects requiring microvascular reconstruction from February 2012 to August 2018 were reviewed. Defects were classified according to their depth as unilaminar (type U = mucosa only), bilaminar (type B = mucosa and bone), or trilaminar (type T = mucosa, bone, and skin) and the number and side of mucosal zones involved (from 1 to 5). Hard palate defects were considered separately and excluded if part of a wider maxillectomy defect. Results: A total of 118 patients were eligible for inclusion in the study. Of type U defects involving 1 mucosal zone, 98% were reconstructed with a radial forearm free flap. Ninety-two percentage of type U defects involving ≥2 mucosal zones were reconstructed with an anterolateral thigh flap. Among type B defects, 86% were reconstructed with a fibula osseocutaneous free flap if less than 4 mucosal zones were involved and 100% reconstructed with an ALT if ≥4 mucosal zones were involved. The algorithm presented was accurate for 93% of the cases. Ninety-eight percentage of patients achieved intelligible speech and 72% returned to a normal diet. Flap success rate was 100%. Conclusions: The algorithm presented provides a simple system to guide the reconstruction of oral cavity defects.