Justin Bieber hired a private island to celebrate his birthday.

The Baby hitmaker turned 21 Sunday and marked the milestone occasion with a lavish celebration on a Caribbean island close to Grenada, TMZ reports.

The singer was joined by a host of pals, including rumoured love interests Hailey Baldwin and Yovanna Ventura, and childhood friend Ryan Butler.

The festivities began late on Saturday evening and continued into Sunday, with the birthday boy appearing to be having a good time. Videos and pictures posted on social media showed him dancing shirtless to 50 Cent's In da Club while clutching a large bottle of champagne.

He later tweeted: "Grateful to be alive! Love u! 21. I love everybody! #21. Thanks for all the birthday love. Grateful for everything. Let's be better this year. Thanks." (sic)

Ahead of his island party, Justin was overjoyed to be presented with a classic 1965 Lincoln Continental by friends John and Sammy Shahidi last week.

A source said the Canadian heartthrob's close pals, who are also his business partners in the selfie-app, Shots, spent approximately $20,000 getting the car completely restored over the past few months.

Justin was clearly thrilled with the gift as he spent much of last Wednesday evening driving it up and down the Sunset Strip in Los Angeles.

The insider said the car looks similar to the one that features in the opening credits of Entourage, which was one of Justin's favourite TV shows.