The singer announced the news on Monday in a social media post, citing the toll she says being in the band has taken on her mental health.
Nelson has been a part of Little Mix since the band’s inception in 2011 on The X Factor, along with Jade Thirlwall, Perrie Edwards, and Leigh-Anne Pinnock.
Describing her nine years with Little Mix as “the most incredible time of my life”, Nelson thanked fans for making her feel “like the luckiest girl in the world”.
“The truth is recently being in the band has really taken a toll on my mental health,” she wrote. “I find the constant pressure of being in a girl group and living up to expectations very hard.”
Nelson added: “There comes a time in life when we need to reinvest in taking care of ourselves rather than focusing on making other people happy, and I feel like now is the time to begin that process.
“So after much consideration and with a heavy heart, I’m announcing I’m leaving Little Mix.”
She thanked “everyone involved in our journey”, including fans and her three former band mates.
Little Mix announced Nelson’s departure on Twitter and expressed support for the singer.
“After an amazing nine years together Jesy has made the decision to leave Little Mix. This is an incredibly sad time for all of us but we are fully supportive of Jesy,” the band shared on its Twitter account.
“We love her very much and agree that it is so important that she does what is right for her mental health and well-being. We are still very much enjoying our Little Mix journey and the three of us are not ready for it to be over.”
The band then appeared to confirm it would continue as a trio, adding: “We’re looking forward to seeing so many of you on tour. Love always, Jade, Perrie and Leigh-Anne xxx”
Little Mix’s sixth studio album, Confetti, came out last month. The Independent deemed it “a glamorous statement of independence” in a four-star review.
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