The United States has achieved significant conservation goals to date, but the loss of biodiversity and ecosystem processes is accelerating. We evaluate opportunities and challenges to conserving our biodiversity by completing a national habitat conservation system, which could stem losses of natural resources and ecosystem services and proactively prepare for climate-change impacts. Lessons learned from two international conservation systems and the infrastructure of national bird conservation partnerships provide examples for completing a national habitat conservation system. One option is to convene a national forum of interested public and private parties to undertake four key actions; develop a common conservation vision and set measureable goals, complete a conservation assessment, use an adaptive management framework to monitor progress toward this vision, and implement strategies to complete a national habitat conservation system. Completing a national habitat conservation system is key to meeting the challenges of conserving habitats and biodiversity of the United States.