The International Slag Valorisation Symposium has become one of the benchmarks in the domain of slag engineering and zero-waste slag valorisation. It aims to contribute towards near zero-waste processing and closed material loops by offering to researchers and industrial actors the opportunity to share knowledge and critically discuss the challenges and opportunities in the field of slag valorisation and by being a fertile ground for new collaborations. To that end, specialists and/or high level representatives of the key institutes in this field from both academia and industry are invited to give a lecture covering a specific topic in a relatively detailed way, striking a balance between scientific depth and relevance as regards industrial application. The content of the Symposium provides a rich overview of the contemporary trends in the worldwide research and innovation strategies as regards the valorisation of ferrous and non-ferrous slag, fly ash, bottom ash and numerous other high-temperature (metallurgical) residues.