Acute severe ulcerative colitis (ASUC) is a medical emergency which is associated with significant morbidity and a mortality rate of 1%. ASUC requires prompt recognition and treatment. Optimal management includes admission to a specialist gastrointestinal unit and joint management with colorectal surgeons. Patients need to be screened for concomitant infections and thromboprophylaxis should be administered to mitigate against the elevated risk of thromboembolism. Corticosteroids are still the preferred initial medical therapy but approximately 30%-40% of patients fail steroid therapy and require rescue medical therapy with either infliximab or cyclosporine. Emergency colectomy is required in a timely manner for patients who fail rescue medical therapy to minimise the risk of adverse post-operative outcomes. We discuss current and emerging evidence in the management of ASUC and outline management approaches for clinicians involved in managing ASUC.