Old-growth grasslands—including savannas and open-canopy woodlands—form over long periods of time and are composed of species adapted to frequent above-ground disturbances. Because many old-growth grasslands occur in places where the climate and soil can also support forests, they are often misunderstood by scientists and undervalued by environmental policymakers and the public. In this talk, I will present the key points of the old-growth grassland concept, supported by the results of global analyses and field-based studies in savannas of the American tropics and subtropics. I will emphasize the common characteristics that can help us to identify old-growth grasslands and how doing so requires us to consider ecological questions about time, stability, and disturbance history. I will argue that to improve the conservation and restoration of grassland biodiversity we should avoid the dichotomy of natural versus anthropogenic disturbance: today, few grasslands are solely maintained by lightning-ignited fires and native megaherbivores and are instead dependent on the management decisions of people. Cultural appreciation for the antiquity of old-growth grasslands—a prerequisite for sustained conservation—should include the value of people who maintain ancient relationships among grassland species, fire, and herbivores.