Social entrepreneur, founder and co-chairman of the board of Natura, a leading Brazilian cosmetics company and one of the world's largest B Corps. Impact investor in new relevant businesses in areas such as forestry management, renewable energy and urban management. Since 2008, through Instituto Arapyaú, a private family foundation, he has been engaged in supporting sustainable development through the articulation of organizations aiming promote the transition for a more just, prosperous and inclusive world. In 2013, he became a B Team Leader of the B Team, a not-for-profit initiative formed by a global group of leaders committed to the belief that the private sector must be considered as a driving force for social, environmental and economic benefit.

Over the last 30 years, Guilherme has participated in the creation and promotion of several organizations such as Fundação Abrinq (Children’s Rights), Ethos Institute (Corporate Social Responsibility), Instituto Akatu (Conscious Consumption), Rede Nossa São Paulo and Rede de Cidades Sustentáveis (Citizenship and Sustainable Urban Development Network). He has also joined the boards of the Brazilian Biodiversity Fund (Funbio) and WWF Brazil. In the 2010 presidential elections, he ran for vice-president for the Green Party, alongside Marina Silva. Leal is a co-founder of RAPS (the Network for Sustainable Politics), an initiative directed at stimulating and preparing new political leaderships for Brazil, and serves as chair at Instituto Natura, committed to improving the quality of public education in Brazil.