PRB is short for:

• Brazilian Republican Party, (Partido Republicano Brasileiro, in Portuguese.
• Pre-Raphaelite Brotherhood, a group of English painters, poets and critics, founded in 1848 by John Everett Millais, Dante Gabriel Rossetti and William Holman Hunt
• Poudrieres Reunies de Belgique, owned by Astra Company
• PRB The Australian Automotive Manufacturer
• PRB = permeable reactive barrier
• Retinoblastoma protein, an important tumor suppressor found mutated in retinoblastoma cancer
• PRB, a gang in Pungo, Virginia that consists of mainly local skateboarders and surfers from Southeast Virginia and North Carolina.