Ryan Lochte -- Comeback Begins ... Locks Down 1st New Sponsor

Ryan Lochte's endorsement comeback is underway ... he just signed a brand new deal with a throat drop company ... TMZ Sports has learned.

Lochte will team up with the Pine Brothers throat lozenge company, a rep confirms -- to be the face of a campaign that promotes the drops as "Forgiving On Your Throat."

Lochte will appear in print ads and a commercial.

Pine Bros. CEO Rider McDowell says, "We all make mistakes, but they're rarely given front-page scrutiny. He’s a great guy who has done incredible work with charities. I’m confident that Pine Bros. fans will support our decision to give Ryan a second chance."

We're guessing the campaign will include some comical references to Lochte's Brazil…