GEM – Grupo de Espeleologia e Montanhismo is a Portuguese group dedicated to exploring caves and promoting mountain and outdoor activities. Based in Alcanena, it brings together people interested in discovering natural environments through practical activities, training, research, and photography. Its programme includes caving, canyoning, via ferrata, hiking, mountaineering, trekking, and technical photography in caves.

GEM offers courses in caving at introductory and advanced levels, canyoning autonomy, and introductory alpinism. Its projects cover cave exploration and documentation, karst studies, climatology, and bat monitoring, with initiatives in locations including Vale da Trave–Moitas Venda, Cabeço dos Alecrineiros, and the Algarve. The group also shares specialist knowledge through news, articles, publications, a newsletter, photographs, videos, and GEM EspeleoRádio.

Visitors can learn about the organisation, its activities, and membership options through its website. GEM also lists member benefits, partnerships, insurance, and equipment rental, supporting participation in its activities and access to the equipment needed for outdoor exploration.