Wild orangutans are primarily arboreal—they spend most of their time high in the trees. They are the only members of the great ape family to spend most of their time off the ground. Their legs are short, but they have long, muscular arms to help them climb. They use their hands and feet to climb, grasping and swaying their way between trees. Orangutans can also walk on two feet, but locomotion on the ground is usually quadrupedal (on four feet). They build a nest of branches and leaves in a tree each evening and also sometimes during the day.

Orangutans are the most solitary of the great apes, but they exhibit a wide range of sociality across their range and may be extremely social when they do associate with other orangutans. Generally, flanged male orangutans spend most of their time alone, while females usually travel with just their dependent infant or juvenile offspring. However, female orangutans do spend some time with other adult females, often relatives. Unflanged males (males that have not developed cheek pads) also associate with females and other unflanged males in times of food abundance. Male orangutans hold large territories that may overlap the territories of several females. Flanged males use their throat sacs to make long calls, a distinctive vocalization that can carry for almost a mile, which announce territory and attract females. Orangutans, like chimpanzees, have been shown to exhibit innovative behavior and social learning.