L. Gilles Sion

L. Gilles Sion


Gilles Sion has practiced law in the cross-border space for 40 years. He received his B.A. in history and economics in 1977 from Cornell University and his J.D. in 1980 from the University of Virginia School of Law. At UVA Law, he was a member of the Virginia Law Review and the Order of the Coif, as well as a Dillard Teaching Fellow. He obtained an LL.M. in 1981 from Harvard Law School, and a masters of comparative law from the Université Libre de Bruxelles in Belgium in 1982.

From 1982 to 2008, Sion was an associate, and then a partner, at Sidley Austin in New York, with a two-year stint in Sidley’s Singapore office. At Sidley, Sion focused initially on international banking and finance, and then on cross-border mergers, acquisitions and joint ventures and general corporate work, including the spin-off in 2001 of the Americas consulting practice of the Big Four accounting firm, KPMG. In 2008, Sion joined KPMG LLP (US) as a principal and its deputy general counsel for transactions. At KPMG, Sion headed a team that handled all contracting with the firm’s clients and suppliers, as well as acquisitions, spin-offs and joint ventures.

He was also active in the establishment, and then expansion, of the regional grouping of KPMG firms in the Americas, as well as in elaborating the KPMG network’s standard global master services agreement and rules for the governance of the organization. He was the lead lawyer in the establishment of KPMG’s first offshoring entity in India and served on that entity’s board of directors for eight years. He retired as a KPMG principal in 2020, remaining an independent consultant on Latin American matters for several months following his retirement.

He has served on the boards of various charitable organizations, including the Belgian American Educational Foundation.