This review consolidates recent evidence on managing renal cell carcinoma (RCC) in patients with solitary kidneys. It provides a comprehensive discussion of evolving strategies in partial nephrectomy—including open, laparoscopic, and particularly robot-assisted partial nephrectomy (RAPN)—along with thermal and advanced ablative therapies, non-surgical options (such as stereotactic ablative body radiotherapy [SABR] and active surveillance [AS]), and emerging neoadjuvant systemic treatments with tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors (ICIs). In addition, the integration of artificial intelligence (AI) for preoperative planning, intraoperative guidance, and postoperative outcome prediction is discussed. Given the limited renal reserve in these patients, preserving functional renal parenchyma is paramount. This multidisciplinary review synthesizes evidence from 2018 to the present and is supported by 70 contemporary references.