Icons of pride and heritage, lions are also troubled: They've lost 90 percent of their population in Africa and Asia in the last 75 years, mostly due to conflict with humans, poaching, and trophy hunting.

A group of nonprofits and tourism companies created World Lion Day to spread awareness about the conservation issues that lions face, raise funds for lion conservation groups, and to celebrate the animal. Organizations including Panthera, Born Free USA, and National Geographic Society's Big Cats Initiative also support the day and its message of conservation. (See 15 intimate portraits of lions.)

Over the years, National Geographic photographers have taken many photographs of lions in their natural habitats. To share the beauty of these vulnerable animals, we put together their most stunning images.