Justin Timberlake Cancels Concert in Ohio for 2nd Time, Blames Flu

Justin Timberlake is not bringing "SexyBack" tonight ... 'cause he's got a nasty case of the flu and can't perform tonight.

The singer-songwriter posted an apology to his Instagram Thursday evening ... telling fans he was heartbroken, but he needed to cancel the show in Columbus, Ohio because he couldn't even get through soundcheck.

He says it kills him to disappoint his fans and all the members of his team who worked so hard to put the show together ... and, he promises everyone will receive refunds for their tickets.

While many online are wishing Justin the best ... we've heard from a fair few fans who aren't happy about the last-minute cancellation -- especially since this is the second time he hasn't been able to go on.

Back in November, JT had to cancel a series of shows while dealing with bronchitis and laryngitis -- and, one of them was in Columbus, Ohio.

Unclear when JT got the flu ... but, clearly he didn't feel like he could go out and perform tonight. We've reached out for clarification on the cancellation, no word back.