The shaka sign, sometimes known as "hang loose", is a gesture often associated with Hawaii and surf culture. It consists of extending the thumb and smallest finger while holding the three middle fingers curled, and gesturing in salutation while presenting the front or back of the hand; the hand may be rotated back and forth for emphasis. The shaka sign was adopted from local Hawaiian culture and customs by visiting surfers in the 1960s, and its use has spread around the world.

Hawaiians use the shaka to convey the "Aloha Spirit", a concept of friendship, understanding, compassion, and solidarity among the various ethnic cultures that reside within Hawaii, lacking a direct semantic to literal translation. The shaka can also be used to express "howzit?", "thanks, eh?", and "all right!" Drivers will often use it on the road to communicate distant greetings and gratitude.

In American Sign Language, the shaka is one of the two signs used to refer to surfing.In California, the shaka sign may be referred to as "hang loose" or "hang ten"- both associated with surfer culture.

The gesture enjoys common use in American hang gliding culture, for both sentiment and word play, in part due to the simultaneous rise of surfing and hang gliding in California in the 1960s and 70s. It is also widely used among skydivers.