During sudden, global crises, when confronted with limited resources and increasing workloads, research ethics committees (RECs) may want to or need to adjust the order in which they perform ethical reviews of research protocols. This guidance is designed to support RECs in addressing three key aspects related to the prioritisation of research protocols during global crises, drawing on lessons learned from the COVID-19 pandemic. First, it assists RECs in determining whether existing prioritisation systems require modification and explores the possible implications of such changes. Then, it details the structural and procedural arrangements necessary to implement new systems of prioritisation. Finally, it outlines the criteria RECs should consider if they choose to revise their prioritisation approach. These guidelines are informed by a global survey of RECs conducted between December 2024 and January 2025 as well as existing literature on research prioritisation during the COVID-19 pandemic (Gelinas et al., 2018; Jayaweera et al., 2021; Sisk & DuBois, 2020; Cornell, 2022; WHO, 2025; Meyer et al., 2021; Paleoudis et al., 2021). To facilitate practical application, reflection questions are included throughout the guidelines to help RECs critically assess their prioritisation processes and prepare for future crises. These questions are designed to encourage proactive planning and support RECs in balancing ethical considerations with operational challenges during global emergencies. This is a preprint and has not undergone a full academic peer review. It is shared to facilitate timely dissemination and feedback.