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All he needs is love -- and he's got it!

Paul McCartney is engaged to marry love Nancy Shevell, his rep confirms to Us Weekly. "It's true!"

The Beatles rocker, 68, proposed to NYC businesswoman Shevell, 51, last weekend "during a romantic candlelit dinner for two," the insider notes -- but Shevell didn't wear her new ring when she hit the red carpet at Monday's massive Met Gala event in NYC. Still, the source says, "they are telling friends" about their happy news.

It will be the third marriage for McCartney. His first wife, Linda, died of cancer at age 56 in 1998; the spouses of 30 years had three children together. The "Let It Be" singer's second 2002 marriage to Heather Mills ended with a messy, expensive 2008 divorce .

He and Shevell began dating in the Hamptons in 2007, while he and Mills were already estranged.

What designer did Shevell wear to Monday's Met bash? Stella McCartney, naturally!