The 27-year-old pop star was rushed to hospital from his home in Seoul but did not regain consciousness and was pronounced dead, according to Korean news agency Yonhap.
The star's cause of death is currently unknown to officials.
Jonghyun's band SHINee was formed in 2008 by the South Korean entertainment company SM Entertainment. The band comprised of five members: Jonghyun, Onew, Key, Minho and Taemin.
The band have been very successful in the world of K-Pop, having released six chart-topping albums in Korea and five in Japan, in addition to embarking on several world tours.
Jonghyun went on to launch a successful solo career in 2015 and collaborated with several other popular Korean artists.
Our thoughts are with Jonghyun's family and friends during this tragic time.
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