Rod Stewart -- Penny Lancaster TURNED DOWN 'Real Housewives'

You won't see Penny Lancaster on the "Real Housewives of Beverly Hills" next season ... 'cause she officially TURNED DOWN the reality show ... this according to her husband Rod Stewart.

As we previously reported, Penny was one of the front-runners to replace Adrienne Maloof and Camille Grammer ... but yesterday at LAX, Rod told us his wife ultimately pulled the plug on the negotiations.

"She doesn't want to do that sort of thing," Stewart said ... adding, "She's just happy being a mom."

Meanwhile, producers are still on the hunt to round out the cast ... and sources tell us former "Extra" host Dayna Devon is still a favorite to make the cut.