Coral reefs are rapidly degrading under escalating local and global pressures and some centennial coral colonies may disappear before they are even documented. These giant colonies embody resistance and resilience in a changing ocean, can archive long-term environmental histories and may hold valuable clues to the traits that have enabled their survival. Yet, coordinated, large-scale information on their distribution, condition and ecology is still lacking. Map the Giants is a global citizen-science initiative launched in 2024 to locate, document and help protect giant coral colonies. This paper has two main aims: first, to synthesise the scientific and practical motivations for focusing on giant corals as both research targets and conservation symbols; and second, to present the design, protocol and operational workflow of Map the Giants. We describe how the project integrates citizen-science principles, user-centred website design, standardised reporting methods and multi-expert validation into a coherent framework, with a public, interactive map and dedicated learning materials to support ocean literacy. Preliminary outcomes from the first 18 months: 195 submissions from 22 countries, of which 133 entries have been validated and added to the public database, demonstrate the feasibility and scientific value of this approach. Contributors routinely exceeded minimum data requirements and high validation rates indicate strong data quality despite heterogeneous participant backgrounds. Together, these elements show that Map the Giants can generate robust, scalable data on giant coral colonies while simultaneously engaging the public, providing a methodological reference for future studies and similar large-scale monitoring initiatives.