G ustav Magnar Witzøe is a Norwegian billionaire who is one of the world's youngest and wealthiest heirs. He is the son of Gustav Witzøe Sr., the founder of SalMar ASA, one of the world's largest and most successful producers of farmed salmon. The company has been at the forefront of industrializing salmon farming, a major industry in Norway.

In 2011, his father transferred the majority of his stake in the publicly traded SalMar to Gustav Magnar, making him a multi-billionaire as a teenager. The move was part of the family's long-term succession planning. While his father remains the operational and strategic leader of the company, Gustav Magnar is the ultimate owner. He is not involved in the day-to-day management of the salmon farming business and has instead focused on his own career as a model and a technology and real estate investor through his private holding company.