Is ROBERT DOWNEY, JR. a henpecked IRONMAN? The truth behind his post-addiction success.

Bob might be a superhero at work, but back home it’s his wife SUSAN who rules the roost with an iron fist.

Insiders say she’s so determined to keep her once-troubled hubby on the straight and narrow that she’s laid down the law in their California homes – a $13 million mansion in Malibu and beach house in Venice – and Robert is more than happy to oblige.

“Bob hears and obeys,” said a pal. “He credits Susan with his success at staying sober and he totally trusts her judgment.”

Robert, 48, and Susan, 39, a noted executive producer, married in 2005 and have a 16-month-old son, Exton. Before they met, Robert’s life was ruled by his addictions. He was arrested on drug charges multiple times, made several attempts at rehab, and ultimately spent a year in jail for violating probation.

“He’s always credited Susan for helping him finally kick his raging drug habit,” said the pal. “He knows that the worst thing about slipping up would be disappointing her – so he

tries not to.”

According to the source, Robert happily does his share of domestic duties to keep their household the way Susan likes it.

“Bob has no problem cooking up a meal if Susan’s stuck at work,” the pal revealed. “He’ll go all out too. He’ll put the baby to bed and then set up the table with candles and flowers to welcome her home.”

Susan is so focused on keeping her husband sober, adds the pal, that she’s even banned some of his friends from their home – including “Transformers” star Shia LaBeouf, who allegedly had a few too many drinks at a party and was hitting on other guests.

“Susan has a onestrike policy,” noted the pal. “She’s not the sort of person you’d want

to mess with. She’s a tough film executive, and she runs her home the same way she does her business ventures – efficiently.

“I wouldn’t go so far as to say Bob’s completely under her thumb, but he certainly does what she says.”