Billy Cranston is a fictional character in the Power Rangers universe. He is the Blue Ranger (triceratops) in the series Mighty Morphin Power Rangers, and was portrayed by actor David Yost. Billy is the only original Power Ranger to remain for the entire MMPR series, and is the second longest-serving Ranger overall behind Tommy Oliver. Until his departure, he is considered the brains of the Power Rangers team, creating many gadgets with which to solve problems that not even Zordon foresees, and he even invents the first team's wrist-worn communication devices. A reimagined version of Billy appears in 2017 reboot film, played by actor RJ Cyler.

Mighty Morphin Power Rangers (MMPR) is an American superhero television series that premiered on August 28, 1993, on the Fox Kids programming block. It is the first entry of the Power Rangers franchise, and became a 1990s pop culture phenomenon along with a large line of toys, action figures, and other merchandise. The show adapted stock footage from the Japanese TV series Kyōryū Sentai Zyuranger (1992–1993), which was the 16th installment of Toei's Super Sentai franchise. The second and third seasons of the show drew elements and stock footage from Gosei Sentai Dairanger and Ninja Sentai Kakuranger, respectively, though the Zyuranger costumes were still used for the lead cast in these two seasons. Only the mecha and the Kiba Ranger costume from Dairanger were featured in the second season while only the Kakuranger mecha was featured in the third season, though the Kakuranger costumes were later used for the mini-series Mighty Morphin Alien Rangers. The series was produced by MMPR Productions and distributed by Saban Entertainment, while the show's merchandise was produced and distributed by Bandai Entertainment.