The ongoing ‘legitimacy crisis’ in investor-State dispute settlement (ISDS) has triggered a comprehensive attempt at multilateral reform. In 2017, Working Group III at the United Nations Commission on International Trade Law (UNCITRAL) was entrusted with a broad, open-ended and problem-driven mandate. The reform process aims to tackle particular concerns with ISDS: excessive costs and lengthy proceedings, inconsistent and incorrect decisions, and a lack of arbitral diversity and independence. The exclusion of substantive treaty reform has met critique but states are considering a wide range of procedural options from incremental reform to a multilateral court, appellate mechanism, and ISDS alternatives. In this article, we introduce the reform process and the seven articles that follow in this Special Issue of the Journal on World and Investment and Trade. In these contributions, ISDS Academic Forum members analyse the basis for each concern and the potential contribution of leading reform models.