The term Marine Animal Forest (MAF) was first described by Alfred Russel Wallace in his book “The Malay Archipelago” in 1869. The term was much later re-introduced and various descriptions of MAFs were presented in great detail as part of a book series. The international research and conservation communities have advocated for the future protection of MAFs and their integration into spatial plans and, in response, there are plans to include the characteristics of MAFs into national policies and international directives and conventions (i.e. IUCN, CBD, OSPAR, HELCOM, Barcelona Convention, European directives, ABJN policies etc.). Some MAF ecosystems are already included in international and national conservation and management initiatives, for instance, shallow water coral reefs (ICRI, ICRAN) or cold-water coral reefs and gardens and sponge aggregations (classified as Vulnerable Marine Ecosystems, VMEs), but not as a group together with other ecosystems with similar ecological roles. Marine Animal Forests can be found in all oceans, from shallow to deep waters. They are composed of megabenthic communities dominated by sessile suspension feeders (such as sponges, corals and bivalves) capable of producing three-dimensional frameworks with structural complexity that provide refuge for other species. MAFs are diverse and often harbour highly endemic communities. Marine animal forests face direct anthropogenic threats and they are not protected in many regions, particularly in deep-sea environments. Even though MAFs have been already described in detail, there are still fundamental knowledge gaps regarding their geographical distribution and functioning. A workshop was dedicated to clarifying the definition of MAFs, characterising their structure and functioning, including delineating the ecosystem services that they provide and the threats upon them. The workshop was organised by Working Group 2 of the EU-COST Action “MAF-WORLD” (hereafter WG2), which is responsible for collating and promoting research on mapping, biogeography and biodiversity of MAFs, to identify and reduce these knowledge gaps. Herein, we report on this workshop and its outputs.