Oncoplastic surgery (OPS) has emerged as a new approach for extending breast conserving surgery (BCS) possibilities, reducing both mastectomy and re-excision rates, while avoiding breast deformities. OPS is based upon the integration of plastic surgery techniques for immediate reshaping after wide excision for breast cancer. A simple guide for choosing the appropriate OPS procedure is not available. To develop an Atlas and guideline for oncoplastic surgery (OPS) to help in patient selection and choice of optimal surgical procedure for breast cancer patients undergoing BCS. We stratify OPS into two levels based on excision volume and the complexity of the reshaping technique. For resections less than 20% of the breast volume (level I OPS), a step-by-step approach allows easy reshaping of the breast. For larger resections (level II OPS), a mammoplasty technique is required. We identified three elements that can be used for patient selection and for determination of the appropriate OPS technique: excision volume, tumor location, and glandular density. For level II techniques, we defined a quadrant per quadrant Atlas that offers a different mammoplasty for each quadrant of the breast. OPS is the "third pathway" between standard BCS and mastectomy. The OPS classification and Atlas improves patient selection and allows a uniform approach for surgeons. It proposes a specific solution for different scenarios and helps improve breast conservation outcomes.