Justin worked on his tan as he relaxed by the pool in Cabo San Lucas, Mexico.
The singer showed off his fantastic abs wearing only his shorts and a straw hat to protect his face from the strong sun.
His girlfriend, Selena Gomez, also spent the holiday in Cabo, so although the pair haven't been photographed together, it's rumored they rang in the new year together.
A source told E! News that the 23-year-old "arrived on Saturday evening and checked into an oceanfront villa 10 minutes away from Selena's villa where she was staying. He and Selena spent time together again. They were very low-key and dressed casually." The insider continued, "They rang in the New Year together and enjoyed watching fireworks over the ocean."
As OK! readers know Justin and Selena dated on and off for 5 years, starting back in 2010 and ending in 2015 before the couple reconciled a couple months ago when the "Boyfriend" singer was snapped entering Selena's house for a church meeting even though she was still dating The Weeknd at the time. Days later, it was announced that she and the Weeknd were splitting, and her and Bieber have been inseparable ever since -- attending hockey games together, having hot and steamy date nights, and even jetting off on holidays together.
The relationship has caused a big riff in Selena's family because her mom, Mandy Teefy, is not happy with the on and off couple getting back together. Teefey reportedly had to check herself into a hospital after having a panic attack over the rekindled relationship. The mom and daughter duo even unfollowed each other on Instagram!
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