Smash Mouth's Steve Harwell Rushed to Hospital, Concert Cancelled

Smash Mouth's scheduled concert Thursday was abruptly cancelled after lead singer Steve Harwell was rushed to the hospital ... TMZ has learned.

Steve tells TMZ the group was doing sound check at the venue when he had trouble breathing and told the tour manager he couldn't perform.  The 50-year-old got in an Uber and told the driver to get to the hospital, STAT.

He says doctors told him he was suffering the effects of cardiomyopathy ... a condition he's had for 2 years. Cardiomyopathy is a form of heart disease where the heart muscle becomes enlarged and weak, making it difficult to pump blood.

Steve says he's been feeling bad for 4 days but he was able to perform until last night. He tells us he has been on oxygen and IV's since being admitted. Doctors also gave him steroids and inhalers.

The condition often flares up because of a virus or drinking. Steve says he was not drinking.

He plans to get out of the hospital around noon Friday and says he'll be good to perform tonight.