Renal cell carcinoma is traditionally managed via a surgical approach. Increasingly, local therapy with radiofrequency and microwave ablation is being utilized as an alternative for patients who may not tolerate a nephrectomy or who refuse one. Although local control rates for small lesions are excellent, they drop off precipitously for lesions over 4 cm. Furthermore, lesions in critical areas such as the renal hilum may be difficult to treat with this method. Stereotactic body radiation therapy (SBRT) has had a long record of treating patients with inoperable tumors in locations such as the lung and central nervous system, and there is increasing evidence that it may be useful for patients with renal cell carcinoma. The recent emergence of MRI-guided radiation therapy allows for direct visualization of tumors during treatment, and may potentially allow clinicians to treat tumors more precisely. This phase I study will treat renal cell carcinoma patients using a combination of MRI-guided stereotactic body radiation therapy and microwave ablation.