Brian Ellner, president of One Strategy Group, is a business leader who guides prominent corporations and brands through the interconnected worlds of politics, government, media and communications. He was named by City & State New York as one of the top 15 key players in the world of New York politics and government and one of the 50 most powerful New Yorkers in communications. Brian was recognized as a 2023 Notable Leader in Advertising, Marketing & PR by Crain's New York Business.

Brian previously led Public Affairs in the U.S. for WPP, the world’s largest creative transformation company, and led Purposeful Communications for BCW, WPP’s premier global corporate communications and public affairs advisory firm.

At WPP Brian focused on building the company’s reputation in the United States with an emphasis on civic engagement in New York where WPP has over 9,000 employees.

At BCW, Brian counseled corporate clients on public affairs and social purpose. He has helped shape the strategy for the passage of the Respect for Marriage Act, the Equal Rights Amendment (ERA) and the Equality Act, recruiting American corporations to support their passage. Brian led WPP’s work with the City of New York and he recently helped launch a campaign to ban assault weapons with Brady. Previously Brian led strategy for Human Right’s Campaigns successful effort to enact marriage equality in New York and he created the Americans for Marriage Equality campaign while providing strategic counsel on the successful ballot marriage wins in Maryland, Minnesota, Maine and Washington State.

Prior to joining WPP and BCW, Brian spent four years at Edelman where he led Public Affairs & Issues Advocacy, advising clients in the finance, government, education, nonprofit, philanthropic, professional sports and transportation spaces. Brian was a senior aide in the administration of Mayor Bloomberg, working with the Department of Education to transform public education. He started his career as an attorney and practiced with Paul, Weiss, Rifkind, Wharton & Garrison and O'Melveny & Myers. He represented media and fashion clients including Calvin Klein, Ralph Lauren and Viacom. 

Brian serves on the Board of Athlete Ally where he helped develop the global Principle 6 campaign in response to Russia’s anti-gay laws during the Sochi Olympics. Brian is a Founding Board Member of the 5BORO Institute, a newly formed policy think tank dedicated to NYC’s revival and he was WPP’s representative to the Partnership for NYC and the Association for a Better New York. Brian was also the executive sponsor for WPP Unite in North America, WPP’s LGBTQ+ ERG. In 2015, Brian was awarded ADCOLOR’S Advocate of the Year.

A graduate of Dartmouth College and Harvard Law School, Brian is a native New Yorker who grew up in Stuyvesant Town and attended New York City's public schools.