Gale Hawthorne is a character from The Hunger Games trilogy and, along with Peeta Mellark, is the love interest of Katniss Everdeen. He is played by Liam Hemsworth in the films.
In The Hunger Game's, Gale's role is pretty minor. He is Katniss's hunting partner, so they could support their famillies. He agrees to support Katniss's family when she goes out to fight in the Hunger Games. In the first book, he and Katniss are not shown to have any romantic feelings for each other. However, in the movie, it is hinted that he has a crush on her, as he looks upset when he sees Katniss kiss Peeta on TV.
In Catching Fire, Gale is jealous of Katniss's relationship with Peeta. He eventually admits this to Katniss, and the two kiss, which leaves Katniss confused about her feelings for Peeta. This kiss is reported to President Snow, who threatens to kill Gale unless Katniss is in love with Peeta. Gale suggests they run away together, so they can be together.
At one point, Gale gets beaten by the districts Peacekeepers, and spends the night at Katniss's house, while her mother tried to heal him. Katniss spends the night at Gale’s side, holding his hand and stroking his face, and even kissing him. However, their plan to run away together is ruined, when Katniss is forced to play in that year's Hunger Games. Katniss does not see Gale for the rest of the book.
In Mockingjay, Gale is part of Katniss's rebellion against the capitol. The two have a lot of chemisty between them, and Katniss doesn't know who she will end up with, Gale or Peeta. In the end, Katniss chooses Peeta, and not Gale.