Background: Vitamin D affects physical performance in older adults. Its effects on muscles, notably on muscle strength, remain unclear. The objective of this cross-sectional study was to determine whether hypovitaminosis D is associated with triceps brachii muscle fatigability in community-dwelling older women. Methods: A randomized subset of 744 women aged >= 75years from the EPIDOS cohort was categorized into two groups according to triceps brachii muscle fatigability, defined as loss of strength > 5% between two consecutive maximal isometric voluntary contractions. Hypovitaminosis D was defined using consensual threshold values (i.e., serum 25-hydroxyvitamin D concentration [25OHD] <= 10 ng/mL, <= 20 ng/mL, and <= 30 ng/mL). Age, body mass index, comorbidities, use psychoactive drugs, physical activity, first triceps strength measure, hyperparathyroidism, serum concentrations of calcium, albumin and creatinine, season and study centers were used as potential confounders. Results: The prevalence of hypovitaminosis D <= 30 ng/mL was greater among women with muscle fatigability compared with the others (P = .009). There was no between-group difference using the other definitions of hypovitaminosis D. The serum 25OHD concentration was inversely associated with the between-test change in triceps strength (adjusted beta = - 0.09 N, P = .04). Hypovitaminosis D <= 30 ng/mL was positively associated with triceps fatigability (adjusted OR = 3.15, P = .02). Conclusions: Vitamin D concentration was inversely associated with the ability to maintain strength over time in this cohort of community-dwelling older women. This is a relevant new orientation of research toward understanding the involvement of vitamin D in muscle function.