The fashion industry is recognized among the most impactful industries in relation to environmental and social damage due to unsustainable models. While countless research studies focus on the supply chain and product innovation, the presented inquiry studies the fashion retail sector with the goal of systematizing existing sustainable practices based on service offerings. We present the results of an extensive case-study analysis conducted on 370 initiatives of different natures gathered among international companies and local actors in the European context that offer services oriented toward sustainability. As a result, we propose an ontology that encompasses three areas (services for environmental sustainability, culture of sustainability, and implementation of social sustainability) and comprehensively describes existing sustainability strategies for helping retailers preserve the environment, while promoting socially inclusive practices and disseminating the culture of sustainability. The innovation of retailing from a similar perspective aims at rendering businesses more resilient to survive market and social transformations, especially in consideration of the boost to sustainable and circular transformation advocated by recent European legislation.