The singer has served as lead vocalist since the band formed in 1997.
A statement from the group’s representative reads: “Kasabian have announced today that Tom Meighan is stepping down from the band by mutual consent.
“Tom has struggled with personal issues that have affected his behaviour for quite some time and now wants to concentrate all his energies on getting his life back on track.
“We will not be commenting further.”
The 39-year-old’s unexpected exit leaves the group without a lead singer.
Meighan, Sergio Pizzorno and bassist Chris Edwards formed the band in 1997 when they attended college together in Leicestershire.
Guitarist and keyboardist Chirs Karloff then joined and the group released their self-titled debut album in 2004.
The record included hits such as Club Foot and Cutt Off, charting at an impressive number four in the UK.
Their most recent release, 2017’s For Crying Out Loud, received positive reviews and gave the band their fifth consecutive number one.
Kasabian has won numerous NME Awards over the years, including the Best Live Band accolade, and one Brit Award, for Best British Group in 2010.
Karloff left the group in 2007 citing “artistic and creative differences.”