RI or ri may refer to:
Richard Milhous Nixon (January 9, 1913 – April 22, 1994) was the 37th President of the United States from 1969 until 1974 and the only president to resign from the position.
The Riemann zeta function or Euler–Riemann zeta function, ζ(s), is a function of a complex variable s that analytically continues the sum of the Dirichlet series
Robyn Rihanna Fenty (; born 20 February 1988) is a Barbadian singer, businesswoman, diplomat, actress, dancer, and songwriter.
Sir Richard Starkey (born 7 July 1940), known professionally as Ringo Starr, is an English musician, singer, songwriter and actor who gained worldwide fame as the drummer for the Beatles.
Rio de Janeiro (; Portuguese: [ˈʁi.u d(ʒi) ʒɐˈnejɾu]; River of January), or simply Rio, is the second-most populous municipality in Brazil and the sixth-most populous in the Americas.
Richard I (8 September 1157 – 6 April 1199) was King of England from 1189 until his death. He also ruled as Duke of Normandy, Aquitaine and Gascony, Lord of Cyprus, Count of Poitiers, Anjou, Maine, and Nantes, and was overlord of Brittany at various times during the same period.
Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics for which he proposed the parton model.