More legal issues for "The Real Housewives of Atlanta" star Kelli Ferrell's ex-husband ... he's been arrested on a theft charge ... and it's a felony.

Kelli's ex, Mark Ferrell, was arrested Tuesday and taken into custody in Georgia on a felony charge of theft by taking ... according to online records.

It looks like the alleged incident happened back in November … but we are still working on the details.

As we first told you ... Kelli and Mark are duking it out in court over child support ... and last year he was thrown in jail after Kelli claimed he had an unpaid balance. He was released after paying her the money.

The Bravo star married Mark in 2011 and filed for divorce in 2022 ... and in September 2024, they finalized their divorce.

Mark's also suing Bravo for defamation over claims made about him on the show.