The restoration of species is one of the most important conservation tools in the context of constantly intensified human-driven global biodiversity loss. The reintroduction/restocking activities are related to significant researches and data gathering before and during the working process, which ensures their sustainable success. 
The aim of this thematic collection is to collate publications, related to reintroduction or restocking of animal and plant species of conservation importance worldwide, including mostly the categories “Research Article”, „Data Paper” and “Species Conservation Profiles”. The collection was initiated after the “International Scientific Conference on Restoration of Conservation-Reliant Species and Habitats” was held in 2020 in the Faculty of biology of Sofia University, but aims to enlarge with similar researches, conducted worldwide.