Serena is the female protagonist of the Kalos based Pokemon games (Pokemon X and Pokemon Y).
Game canon
If chosen by the player, Serena starts as a young girl who recently moved to Vaniville Town with her mother,
Grace. She makes friends with the neighborhood kids:
Calem,
Shauna,
Tierno, and
Trevor, and they're all chosen to get a starter and asked to complete the Pokedex by
Professor Sycamore. From then on, she travels the Kalos region, beating Gym Leaders, taking down Team Flare, and eventually becoming Champion of the region. She (the player) can also become Grand Dutchess if she choses to do so.
If not chosen by the player, Serena is replaced with Calem as one of the neighborhood rivals already from Vaniville Town. The list of Pokémon she owns in X and Y consist of
Fletchling, Espurr, Meowstic, Absol, Altaria, and Clefable. She will also have Jolteon, Serena's Fennekin, Serena's Braixen, and Delphox if the player chooses Grass, Flareon, Froakie, Frogadier, and Serena's Greninja if the player chooses Fire, or Vaporeon, Chespin, Quilladin, and Chesnaught if the player chooses Water.
Serena appears in
Pokemon Masters EX. She's very cheerful and loves fashion, but also shows a calm and serious side during battle. Serena's starter Pokémon is chosen to be Fennekin, which can evolve into Braixen, and then Delphox. However, in her Palentine's Day 2021 special outfit, she owns a Whimsicott. In her Sygna Suit, she cuts her hair and befriends Zygarde, working to protect Pasio.
Pokémon the Series
Serena is a young girl who just started on her journey as a Pokémon trainer in the Kalos region. Prior to the events of the first episode, she had met Ash three years prior in Professor Oak's Summer Camp in Kanto, and when she saw him in Lumiose City on TV, decided to go chase him down, and follow in his footsteps as a trainer as well as a Pokémon Coordinator, instead of becoming a Rhyhorn Racer like her mother.
GOTCHA!
Serena makes a cameo in this animated music video, fighting Mega Mewtwo Y. Her partner in this canon is Froakie, which has since evolved into Greninja.