Rb or RB may stand for:
In science and computing:
- Rebar (short for reinforcing bar), also known as reinforcing steel, reinforcement steel, a common steel bar, and is used in reinforced concrete structures
- Retinoblastoma, a childhood cancer of the eyes caused by a mutation in the retinoblastoma protein
- Retinoblastoma protein, a tumor suppressor protein
- Rubidium, a chemical element
- .rb, the file extension for documents created in Ruby or in REAL Basic
In transport and vehicles:
- RB, the IATA airline code for Syrian Arab Airlines
- re-entry body, the United States Air Force term for a re-entry vehicle
- Hyundai RB (buses), a series of Korean buses
- Nissan RB engine, a gasoline engine made by Nissan
- Réseau Breton, a French railway network in Brittany
- SJ Rb, a Swedish locomotive
- Regionalbahn, a type of train in Germany
In other uses:
- R. B. (nickname)
- Parti de la Renaissance du Bénin or Benin Rebirth Party, a political party in Benin
- Radio Bremen (RB), public broadcaster for the German state of Bremen
- Rancho Bernardo, a community in San Diego, California, United States
- Reckitt Benckiser, a company in United Kingdom
- Running back, a position in North America football
- Right back, a defensive position in association football
- Ray-Ban, a sunglasses company
- Rock Band, a music video game series or Rock Band (video game), the game of the same name
- Rebecca Black, an American pop star
- Rupiah Banda, current President of Zambia
- República Bolivariana, Spanish-language phrase for the type of government in Venezuela.
- "Riding Buddy", a term of endearment used in British Columbia to identify one's favourite mountain biking partner.
- Regional Bulletin, a method of sending updates to all employees.
- The logo and initials for Rankin/Bass.
- R. B. Winter State Park, a park in Pennsylvania
- R&B, a popular music genre combining blues, gospel and jazz influences.