ALEC BALDWIN’s pregnant young wife has a message for Lindsay Lohan: Keep your hands off my man!

The warning comes after 26-year-old Lindsay saw Alec, 55, perform in the Broadway play “Orphans” and paid him a surprise visit backstage.

“Lindsay was a gushing mess when she congratulated Alec,” a source close to the “30 Rock” Emmy winner told The ENQUIRER. “She was all over him, telling him how brilliant he is and how much she admires him.

“And he was lapping it up.”

But when Alec’s new bride, 29-year-old yoga instructor Hilaria, found out about the cozy meeting, insiders say she hit the roof – and warned Alec to stay away from the “Mean Girls” star.

“Hilaria was furious when she heard how touchy-feely Lindsay was, and Alec pretty much walked into a hornet’s nest when he got home that night,” the source continued. “She’s smart enough to know that Lindsay is a desperate woman on the hunt for a sugar daddy – or at the very least a badly needed career boost – and she’s outraged that Lindsay would show up like that and flirt outrageously with her husband while she’s pregnant with their baby.”

Hilaria, who mar­ried Alec last June, still has full faith in her hubby, says the source – but she doesn’t trust Lindsay at all.

“Hilaria’s con­vinced Lindsay would stop at noth­ing to get her claws into someone with as much clout as Alec,” noted the source. “And she doesn’t want Alec to even be in the same room with her.”

But Hilaria should at least be able to rest easy for a while, see­ing how Lindsay started serving a 90-day court ordered rehab stay at the Betty Ford Clinic.