Joe Manganiello and fiancée Caitlin O’Connor are leveling up after their engagement — ditching L.A. and settling into a slower life … all because they’ve got babies on the brain.

Sources close to the couple tell TMZ Joe and Caitlin packed up for their native Pittsburgh … officially swapping Hollywood for a place in Joe’s hometown of Mt. Lebanon.

We’re told the move came after they realized they wanted to be closer to family — and figured Pittsburgh would be the perfect place to raise kids … when that time rolls around.

Despite the pair making Pittsburgh a solid home base, they still plan to bounce to NYC and L.A. for work commitments.

We’re also told they’re hyped to hit Steelers games every week … which, aside from the whole family-planning thing, was a major selling point.