Jerome Valeska is one of the main antagonists of the TV series Gotham. He appears as a minor antagonist in the first season of the the series, and also one of the main antagonists (alongside Theo and Tabitha Galavan) in Rise of the Villains, and the true main antagonist in the Mad City arc, as well as the secondary main antagonist of the third season. and the show's incarnation of The Joker. Jerome worked at the carnival with the Flying Graysons before having revealed to have committed matricide due to his mother being a "nagging drunken whore".

After having been busted out of Arkham Asylum, Jerome was offered the chance to wreak havoc in Gotham in the Season 2 opening story arc Rise of the Villains. As the leader of the Maniax, Jerome terrorized the whole of Gotham. Although he was betrayed and killed by his boss Theo Galavan (who wanted to be seen as a hero to the city), Jerome left a legacy leading to some citizens to follow his example, causing a fanatical cult to plot his resurrection. A year following his death, Jerome's reanimation was a success and Jerome ignited a bomb which blew up Gotham's power grid, causing a city-wide blackout and plunging the city into darkness and anarchy.

He was portrayed by Cameron Monaghan, who is best known for portaying Ian Gallagher on the Showtime comedy-drama Shameless.