Sydney Sweeney Arrives for Boxing Movie Premiere With Christy Martin

Sydney Sweeney's getting ready for the first showing of her boxing movie chronicling the life of legendary boxer Christy Martin ... and she's looking like a total knockout.

The actress just arrived at the Princess of Wales Theatre at the Toronto International Film Festival for the premiere of her film, "Christy."

Sydney's all glammed up and spilling out of the top of her dress, which is hugging her slim figure.

Christy's in the house too ... and they signed a boxing glove together as they posed for photos in front of a huge throng of fans.

As we told you ... Sydney's movie has "tested through the roof," and folks who have seen her in the flick say this could be the role that earns her the first Oscar win of her career.

Sydney gained 40 lbs to play Christy on the big screen ... and now a select few are going to see all the hard work she poured into telling Christy's story.

The movie's dropping at just the right time for Sydney ... she's the hottest thing in marketing right now, thanks to a bunch of ad campaigns with American Eagle and Jimmy Choo ... hell, folks are even buying her used bathwater.