This randomized controlled trial (RCT) with 160 patients suffering from fatigue afterCOVID-19 infection aims to investigate the effectiveness of the unguided digitaltherapeutic vimida for reducing post-COVID-19 fatigue. Inclusion criteria are: male,female or non-binary, age ≥18 years, diagnosis of post-COVID-19 fatigue, ≥3 months sincethe last infection with COVID-19, fatigue severity score (cut-off) of ≥ 16 on the ChalderFatigue Scale (CFQ-11), consent to participation, and sufficient German language skills.Exclusion criteria are a known psychiatric or somatic condition that can explain thefatigue and current participation in a multidisciplinary rehabilitation program aimed toameliorate the consequences of COVID-19.Patients will be randomized and allocated to either an intervention group, in which theywill receive access to vimida in addition to treatment as usual (TAU; n=80), or to acontrol group, in which they will receive access to TAU only (n=80).The primary endpoint will be fatigue symptoms with three months post-allocation (T1)being the primary time point for assessment of effectiveness. Six months post-allocation(T2) will be used as follow-up assessment of endpoints. Secondary endpoints will bedepressive symptoms, mental health-related quality of life, work/social functioning,somatic symptoms, and anxiety symptoms.