This is a Phase I/II, open-label, multi-center study of axitinib in combination with nivolumab in patients with previously treated and untreated advanced RCC. This clinical study will be composed of a dose finding phase (Phase I) and two parallel dose expansion phases (Phase II). The dose finding phase will assess the safety of the combination and establish a recommended phase II dose (RP2D, the highest tested dose that is declared safe and tolerable by the Investigators and the Sponsor Investigator) in patients with advanced RCC who have received prior systemic therapy for metastatic disease. Phase II will evaluate the efficacy of the combination at the RP2D in two parallel expansion cohorts in both previously treated and treatment naïve patients.