Introduction Hallux rigidus is a common problem of pain and stiffness of the first metatarsophalangeal joint (MTPJ) caused mainly by degenerative osteoarthritis. Several operative techniques have been introduced for the treatment of this condition without high-quality evidence comparing surgical to non-surgical care. In this trial, the most common surgical procedure, arthrodesis, will be compared with watchful waiting in the management of hallux rigidus. Methods and analysis Ninety patients (40 years or older) with symptomatic first MTPJ osteoarthritis will be randomised to arthrodesis or watchful waiting in a ratio of 1:1. The primary outcome will be pain during walking, assessed using the 0-10 Numerical Rating Scale (NRS) at 1 year after randomisation. The secondary outcomes will be pain at rest (NRS), physical function (Manchester-Oxford Foot Questionnaire), patient satisfaction in terms of the patient-acceptable symptom state, health-related quality of life (EQ-5D-5L), activity level (The Foot and Ankle Ability Measure Sports subscale), use of analgesics or orthoses and the rate of complications. Our null hypothesis is that there will be no difference equal to or greater than the minimal important difference of the primary outcome measure between arthrodesis and watchful waiting. Our primary analysis follows an intention-to-treat principle. Ethics and dissemination The study protocol has been approved by the Ethics Committee of Helsinki and Uusimaa Hospital District, Finland. Written informed consent will be obtained from all the participants. We will disseminate the findings of this study through peer-reviewed publications and conference presentations. Protocol version 21 June 2021 V.2.0. Trial registration number NCT04590313.