BACKGROUND: Since 2004, the Weill Cornell Fellowship in Skull Base and Microneurosurgery has provided surgeons from around the world with structured, proficiency-driven instruction in complex skull base anatomy, approaches, and techniques in a lab-based setting. We report on the design of this program, review the factors that have contributed to its success, and evaluate its impact on 200 neurosurgeon-alumni over the past 20 years. METHODS: The 6-12-month fellowship program is tuition-free and open to surgeons worldwide, from senior residents to mid-career surgeons. The program consists of an initial 3 months of training in skull base surgical anatomy, followed by 3-9 months of training in skull base surgical approaches and techniques. All training is closely supervised and follows a standardized sequential dissection curriculum covering the entirety of the skull base. In order to assess the effectiveness and impact of the fellowship program, all alumni were asked to complete a detailed anonymous survey reflecting on their experience and its influence on their surgical abilities and careers. RESULTS: As of January 2025, 200 neurosurgeons from 57 countries have completed the fellowship program, of which 170 were reachable and 133 (78.2%) completed the survey. Respondents indicated a substantial 58.8% increase in their overall neurosurgical skills, abilities, and armamentarium following the fellowship. A significant increase in specific surgical skills was similarly found post-fellowship, with the greatest improvements in navigating the skull base (80.4%), skull base techniques (74.7%), and complications management (70.4%). Overall confidence in performing skull base approaches increased by 50.8%, with the greatest improvements seen in lateral (76.6%) and posterolateral approaches (78.8%). Overall confidence as a neurosurgeon increased by a notable 50.8%, and there was strong agreement that the fellowship was fundamental to their neurosurgery training and made them better neurosurgeons. 98.5% would recommend the program to other neurosurgeons. CONCLUSIONS: The lab-based Weill Cornell Fellowship in Skull Base and Microneurosurgery has had a profound and positive impact on its alumni, significantly enhancing their surgical skills and careers. The substantial degree of increases in perceived skills and abilities gained following the fellowship are especially notable given the fellowship's limited duration and are evidence that this model of focused, supervised training could serve as a global benchmark for skills-based neurosurgical training.