Mario Leißner, born in 1971, is a lawyer and entrepreneur. After studying and training in Germany and the USA, he spent more than 26 years advising the German and international real estate and fund industry on the structuring and launch of funds, regulatory law and German and international real estate transactions. After heading the legal and tax department of the market-leading Sal. Oppenheim real estate investment company for several years, he founded the first continental European office of King & Spalding LLP, one of the leading international commercial law firms, in 2007.

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As German Managing Partner of the firm and head of the German real estate and funds practice, which won several awards with him, Mario Leissner led the firm to its continued market leadership in advising real estate funds. In 2022, he retired from operational professional activity for health reasons.

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Mario Leißner is considered one of the most renowned German lawyers ("Germany's Best Lawyers" since 2015) with the highest international rankings as well as one of the "leading minds in the German real estate industry" (immobilienmanager "Hall of Fame"). Today, he is selectively active as a supervisory board member, consultant and non-executive director.