BACKGROUND: Frailty is common in older people and is characterised by decline across multiple body systems, causing decreased physiological reserve and increased vulnerability to adverse health outcomes. It is estimated that 21% of the community-dwelling population over 65 years are frail. Frailty is independently predictive of falls, worsening mobility, deteriorating functioning, impaired activities of daily living, and death. The World Health Organization's International Classification of Functioning, Disability and Health (ICF) defines mobility as: changing and maintaining a body position, walking, and moving. Common interventions used to increase mobility include functional exercises, such as sit-to-stand, walking, or stepping practice. OBJECTIVES: To summarise the evidence for the benefits and safety of mobility training on overall functioning and mobility in frail older people living in the community. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, AMED, PEDro, US National Institutes of Health Ongoing Trials Register, and the World Health Organization International Clinical Trials Registry Platform (June 2021). SELECTION CRITERIA: We included randomised controlled trials (RCTs) evaluating the effects of mobility training on mobility and function in frail people aged 65+ years living in the community. We defined community as those residing either at home or in places that do not provide rehabilitative services or residential health-related care, for example, retirement villages, sheltered housing, or hostels.  DATA COLLECTION AND ANALYSIS: We undertook an 'umbrella' comparison of all types of mobility training versus control. MAIN RESULTS: This review included 12 RCTs, with 1317 participants, carried out in 9 countries. The median number of participants in the trials was 97. The mean age of the included participants was 82 years. The majority of trials had unclear or high risk of bias for one or more items. All trials compared mobility training with a control intervention (defined as one that is not thought to improve mobility, such as general health education, social visits, very gentle exercise, or "sham" exercise not expected to impact on mobility). High-certainty evidence showed that mobility training improves the level of mobility upon completion of the intervention period. The mean mobility score was 4.69 in the control group, and with mobility training, this score improved by 1.00 point (95% confidence interval (CI) 0.51 to 1.51) on the Short Physical Performance Battery (on a scale of 0 to 12; higher scores indicate better mobility levels) (12 studies, 1151 participants). This is a clinically significant change (minimum clinically important difference: 0.5 points; absolute improvement of 8% (4% higher to 13% higher); number needed to treat for an additional beneficial outcome (NNTB) 5 (95% CI 3.00 to 9.00)). This benefit was maintained at six months post-intervention. Moderate-certainty evidence (downgraded for inconsistency) showed that mobility training likely improves the level of functioning upon completion of the intervention. The mean function score was 86.1 in the control group, and with mobility training, this score improved by 8.58 points (95% CI 3.00 to 14.30) on the Barthel Index (on a scale of 0 to 100; higher scores indicate better functioning levels) (9 studies, 916 participants) (absolute improvement of 9% (3% higher to 14% higher)). This result did not reach clinical significance (9.8 points). This benefit did not appear to be maintained six months after the intervention. We are uncertain of the effect of mobility training on adverse events as we assessed the certainty of the evidence as very low (downgraded one level for imprecision and two levels for bias). The number of events was 771 per 1000 in the control group and 562 per 1000 in the group with mobility training (risk ratio (RR) 0.74, 95% CI 0.63 to 0.88; 2 studies, 225 participants) (absolute difference of 19% fewer (9% fewer to 26% fewer)). Mobility training may result in little to no difference in the number of people who are admitted to nursing care facilities at the end of the intervention period as the 95% confidence interval includes the possibility of both a reduced and increased number of admissions to nursing care facilities (low-certainty evidence, downgraded for imprecision and bias). The number of events was 248 per 1000 in the control group and 208 per 1000 in the group with mobility training (RR 0.84, 95% CI 0.53 to 1.34; 1 study, 241 participants) (absolute difference of 4% fewer (8% more to 12% fewer)). Mobility training may result in little to no difference in the number of people who fall as the 95% confidence interval includes the possibility of both a reduced and increased number of fallers (low-certainty evidence, downgraded for imprecision and study design limitations). The number of events was 573 per 1000 in the control group and 584 per 1000 in the group with mobility training (RR 1.02, 95% CI 0.87 to 1.20; 2 studies, 425 participants) (absolute improvement of 1% (12% more to 7% fewer)). Mobility training probably results in little to no difference in the death rate at the end of the intervention period as the 95% confidence interval includes the possibility of both a reduced and increased death rate (moderate-certainty evidence, downgraded for bias). The number of events was 51 per 1000 in the control group and 59 per 1000 in the group with mobility training (RR 1.16, 95% CI 0.64 to 2.10; 6 studies, 747 participants) (absolute improvement of 1% (6% more to 2% fewer)). AUTHORS' CONCLUSIONS: The data in the review supports the use of mobility training for improving mobility in a frail community-dwelling older population. High-certainty evidence shows that compared to control, mobility training improves the level of mobility, and moderate-certainty evidence shows it may improve the level of functioning in frail community-dwelling older people. There is moderate-certainty evidence that the improvement in mobility continues six months post-intervention. Mobility training may make little to no difference to the number of people who fall or are admitted to nursing care facilities, or to the death rate. We are unsure of the effect on adverse events as the certainty of evidence was very low.