Mayor Undersee was the mayor of District 12.
A fairly just mayor, Mayor Undersee attempted to improve District 12, a district that had many problems and affairs. He opened each reaping with his usual speech along with the district's escort, Effie Trinket.
The mayor was not very strict about enforcing laws and didn't have a taste for events such as public punishments. He also regularly bought strawberries from Katniss Everdeen and Gale Hawthorne, even though their gathering of the fruit was technically illegal.
In Catching Fire, Katniss looks into Mayor Undersee's office, wanting to say hello, but he is not there. Instead, Katniss learns - via the unsupervised television - about the uprising in District 8.
Mayor Undersee was described as being a tall, balding man.