The Molehill Mob is a fictional criminal gang featured in the Batman multimedia franchise. Specifically, it is associated with the original live-action Batman television series that aired on ABC from 1966 to 1968. It first appeared in the series' pilot episode, "Hi Diddle Riddle".
The Molehill Mob was a gang of common hoods, thugs and henchmen, all of whom worked for the costumed criminal known as the Riddler. The only members of the group identified by name were Harry and Molly, the latter of whom was more of a gun-moll and a distraction than an active member, though she did play a vital if albeit tragic role in one of the Riddler's more fiendish plots. 
The Molehill Mob were based out of Gotham City, but never stayed in one place for too long a period of time. They occupied a subterranean chamber beneath Glover Street for a time, but were forced to vacate after a run-in with Batman and Robin.
The Riddler later captured Robin and made a facial impression of him, which was then used to create a clever mask. Molly wore a Robin costume and donned a mask in order to trap the Batman. Ultimately, this plan failed, resulting in Molly's demise. After freeing Robin, the Batman had a second run-in with the Molehill Mob at the Gotham City World's Fair, where they fought up against them in a pavilion dedicated to the Republic of Moldavia. During the fight, an explosion erupted, which seemingly took the Riddler's life. 
Though believed dead, the Riddler did in fact survive to plague the Dynamic Duo another time. He was always certain to have an ever-growing and ever-expendable group of henchmen to follow his instruction.
- The concept behind the Molehill Mob was created by teleplay writer Lorenzo Semple, Jr. and director Robert Butler.
- The Molehill Mob is based on a DC Comics organization by the same name, which appeared in Batman, Volume 1 #171 in May, 1965.