IntroductionSystemic sclerosis (SSc) is an autoimmune disease characterised by inflammation, fibrosis and vasculopathy. Digital ulcers (DUs) are a frequent manifestation of vasculopathy in patients with SSc. Despite recent advances in pharmacological treatments, DU still have major health and economic implications. As there is currently no proven therapeutic strategy to promote DU healing, new treatments are urgently needed. Mesenchymal stem or stromal cells (MSCs) may provide a novel therapy for DU in SSc, because of their immunomodulatory and vasculoregenerative properties. Allogeneic MSC therapy involves functionally competent MSCs from healthy donors and may be used as ‘off-the-shelf’ available treatment. This study will evaluate whether allogeneic MSC therapy is a safe and potentially efficacious treatment for DU of SSc.Methods and analysisThe MANUS (Mesenchymal stromal cells forAngiogenesis andNeovascularization in digitalUlcers ofSystemic Sclerosis) Trial is a double-blind randomised placebo-controlled trial. 20 patients with SSc with refractory DU will be randomised to receive eight intramuscular injections with either placebo or 50*10⁶MSCs. The primary outcome is the toxicity of the treatment at 12 weeks after administration. Secondary outcomes include (serious) adverse events, number and time to healing of DU, pain, reported hand function, quality of life and SSc disease activity. We will also evaluate changes in nailfold capillaroscopy pattern, as well as biochemical parameters and biomarkers in peripheral blood and skin biopsies. Follow-up visits will be scheduled at 48 hours and 2, 4, 8, 12, 24 and 52 weeks post-treatment. If the results confirm safety, feasibility and potential efficacy, a large multicentre randomised controlled trial with longer follow-up will be initiated focusing on efficacy.Ethics and disseminationThe study has been approved by the Dutch Central Committee on Research Concerning Human Subjects (protocol no: NL51705.000.15). The results will be disseminated through patient associations and conventional scientific channels.Trial registration numberNCT03211793; Pre-results.