EN
This article explores the process of providing social and solidarity economy (SSE) in transition to sustainable development. The notion of sustainability as the state of the triad of three interrelated and interdependent systems: socio-economic, biological human nature, ecological is grounded.It reveals the meaning and content of SSE. It reveals the principles that underlie the functioning of solidarity economy structures and experience to ensure SSE in the EU.It explores the experience of the internal networks of the European initiatives on morality, national solidarity and territorial networks in Europe and Intercontinental network promoting SSE. The article grounds the necessity to use the experience of the European Union to ensure sustainable development in terms of development SSE projects, which in turn would contribute to solving urgent social, economic and environmental problems.