Zac Sunderland looks out the hatch of his yatch on Monday in San Diego, one of the last stops on his 45,060-kilometre trip around the world. (Lenny Ignelzi/Associated Press)

A shaggy-haired 17-year-old from Southern California has become the youngest person to sail around the world alone.

Zac Sunderland docked Thursday in Marina del Rey, a coastal community west of Los Angeles, completing a 45,060-kilometre trip that began last year.

His family, friends and hundreds of curious onlookers cheered as his 11-metre Intrepid sailboat entered the harbour.

He later gave a whoop of joy as he approached a microphone to address the crowd.

"It's awesome to finally get back here," he said.

Zac Sunderland's yacht Intrepid seen in the Panama Canal on May 19. (Alberto Lowe/Reuters)

Sunderland was 16 when he left Marina del Rey on June 14, 2008 — a voyage that included encounters with pirates and wild storms. His father is a shipwright who has met him at various stops around the world, often to help him repair damage to the boat.

On Sunderland's website, a series of videos documents his travels.

In one video, Sunderland tells the camera he's about to sail into a "massive squall," adding, "I need to just put away all the sails right now, so I gotta go."

Sunderland's record may not last for long.

British sailor Mike Perham is a few months younger than Sunderland and is sailing a bigger, faster boat in an attempt for the record.

The record was previously held by an Australian who was over 18 when he completed the voyage in 1996.