The 27-year-old shared the good news last night (25 January) when he tweeted a picture of himself with Chloe's jewelled hand over his mouth.
Alongside the picture, JB wrote: "She said yes... #chlobeengaged x."
Friends and fans rushed to congratulate them on social media, including fellow JLS star Aston Merrygold, who said: "couldn't keep that secret any longer finally!!!! so happy for you both! #love #oooowegunaparty."
JB's girlfriend of five years, Chloe also took to Twitter to express her joy.
Posting a picture of her beautifully manicured fingers, with the huge sparkler on her ring finger, she wrote: "Can't believe I'm engaged! Love @JBGill so much! X."
Croydon-born JB meanwhile thanks fans for their kind messages, saying: "Thank you all so much for your congratulations and lovely comments.been an amazing day!!keep you all posted...hehe goodnight, God bless x."
This morning, he admitted he felt "very blessed" and shared his "amazement" at the fact that #chlobeengaged was trending worldwide.
JB and Chloe bought an 11-acre estate last year and he is soon to start an agricultural management course to pursue his interest in farming.
JB has also teamed up with DJ and music producer Charlie Hedges to release his debut solo single, dance track 'Best Night Of My Life', making him the first member of JLS to release solo material since they split.
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Listen to JB Gill's collaboration with Charlie Hedges, 'Best Night Of My Life':