OBJECTIVE: To describe the protocol and statistical analysis plan for the Treatment of Invasively Ventilated Adults with Early Activity and Mobilisation (TEAM III) trial. DESIGN: An international, multicentre, parallel-group, randomised controlled phase 3 trial. SETTING: Intensive care units (ICUs) in Australia, New Zealand, Germany, Ireland, the United Kingdom and Brazil. PATIENTS: 750 adult patients expected to receive mechanical ventilation for more than 48 hours. INTERVENTIONS: Early activity and mobilisation delivered to critically ill patients in an ICU for up to 28 days compared with standard care. MAIN OUTCOME MEASURES: The primary outcome is the number of days alive and out of hospital at 180 days after randomisation. Secondary outcomes include ICU-free days, ventilator-free days, delirium-free days, all-cause mortality at 28 and 180 days after randomisation, and functional outcome at 180 days after randomisation. RESULTS: Recruitment at 46 research sites passed 576 patients in March 2021. Final collection of all 180-day outcome data for the target of 750 patients is anticipated by May 2022. CONCLUSIONS: Consistent with international guidelines, a detailed protocol and prospective analysis plan has been developed for the TEAM III trial. This plan specifies the statistical models for evaluating primary and secondary outcomes, defines covariates for adjusted analyses, and defines methods for exploratory analyses. Application of this protocol and statistical analysis plan to the forthcoming TEAM III trial will facilitate unbiased analyses of the clinical data collected. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT03133377.