Background/Objectives: Masters athletes are adults aged ≥40 who compete in sport, exhibiting superior physical function and healthier aging than their sedentary peers. However, even highly trained masters athletes experience age-related performance declines. Women masters athletes represent a growing yet understudied population who may face unique physiological challenges. This scoping review synthesizes literature from 1984 to 2024, examining the impact of age and menopause on determinants of endurance performance in women masters athletes. Methods: Following JBI scoping review methodology, six databases were searched (Medline, Embase, Central, CINAHL, SPORTdiscus, Scopus). Studies were evaluated for population characteristics, methodological approaches, and physiological determinants of performance (i.e., aerobic capacity, lactate kinetics, and exercise economy). Results: Twenty-nine studies were included. Most (n = 28) assessed aerobic capacity, reporting declines between 0.36 and 0.84 mL·kg-1·min-1·year-1 (0.5-2.4%·year-1). These reductions were primarily associated with decreased cardiac output followed by changes in body composition. Training volume emerged as a predictor of aerobic capacity, but the effects of menopause were unclear. Findings on lactate kinetics and exercise economy were mixed but preliminary research indicated that lactate threshold relative to VO2max generally increased, peak lactate remained stable and energy cost increased with age. Fitness and health characteristics among women athletes differed from sedentary populations, emphasizing the need for athlete-specific data to support training and health decisions. Conclusions: Aging is associated with decreased aerobic capacity and variable changes in lactate kinetics and exercise economy. While training volume may attenuate performance decrements, the impact of menopause remains uncertain, underscoring the need for longitudinal research to better support this growing segment of the population.