This thesis investigates the lifelong learning ecologies that combine formal, non-formal, and informal learning to foster understanding and participation in the new Holocaust memory landscapes shaped by digital technologies. Stemming from an analysis of the relationships between post-witness historical memory and the emerging media ecosystems that transmit and share these memories, the dissertation deepens its exploration of educational approaches and places the focus on lifelong learning ecologies as an effective approach for both the general public and teachers’ professional learning on the topic. This dissertation investigated two parallel streams of research: the (social) media ecosystems of Holocaust memory as deployed on social media by Holocaust organisations such as museums and memorials, and the learning ecologies of online users who seek to create meaningful learning experiences related to the Holocaust. The thesis is presented as a compendium of seven papers and one supplementary study.