Citizens Coordinate for Century 3 (C3) is a nonpartisan, nonprofit organization of informed citizens interested in regional planning issues, preservation, and revitalization of downtown San Diego.

C3 was founded in 1961 by Lloyd Ruocco and Esther Scott with the support of Hamilton Marston and Ellen Revelle. Their objectives were to conserve and promote "a handsome & functional community" through research, education and coordinated citizen action.

C3 Mission Statement:  To establish a nonpartisan, nonprofit organization of informed citizens which will strive for the conservation and improvement of the San Diego region.  To present objective information, constructive opinion, and educational programs reflecting the deliberation of its members.  To weigh all matters in view of the contribution toward achieving the highest standards of environmental quality, physical design, economic benefit, and social progress.

C3 is governed by a Board of Directors and has member Committees to manage events and to address issues of Equity in Planning, Sustainability, Parks & Open Space, Water & Energy, and the Waterfront.
C3 Founder Ellen Revelle