Diane Keaton's L.A. Estate Sells for $18 Million

Diane Keaton's "Three Little Pigs"-inspired Los Angeles mansion officially has a new owner ... and it sold for $18 million.

TMZ has learned the deal has closed on the sprawling 9,219-square-foot estate ... with the sale price coming in $5 million below its most recent asking price and nearly $11 million under the original $28.9 million listing.

As we previously reported ... a buyer was found last month after the property went under contract. It had returned to the market in June for just under $23 million following several price cuts and a removal.

The 5-bedroom, 8-bathroom home was inspired by Diane's childhood love of "The Three Little Pigs" ... an influence perhaps best seen in the 75,000 hand-selected 18th-century bricks sourced from Chicago that form the property's foundation.

The kitchen -- which Diane considered the "heartbeat of the house" -- includes a custom-built island, chicken-wire cabinetry and pendant lights repurposed from a former chicken coop.

"Million Dollar Listing Los Angeles" star Josh Flagg of Compass represented the listing ... while Emil Schneeman of Berkshire Hathaway represented the buyer.