Ramon Berenguer I el Vell ("the Old") was Count of Barcelona in 1035-1076. He promulgated the earliest versions of a written code of Catalan law, the Usages of Barcelona .

Born in 1024, he succeeded his father, Berenguer Ramon the Crooked in 1035. It is during his reign that the dominant position of Barcelona among other Catalan counties became evident.

Ramon Berenguer campaigned against the Moors, extending his dominions as far west as Barbastro and imposing heavy tributes (parias) on other Moorish cities. Historians claim that those tributes helped create the first wave of prosperity in Catalan history. During his reign Catalan maritime power started to be felt in Western Mediterranean. Ramon Berenguer the Old was also the first count of Catalonia to acquire lands (counties of Carcassonne and Razés) and influence north of the Pyrenees.

Another major achievement of his was beginning of codification of Catalan law in the written Usatges or Usatici of Barcelona which was to become the first full compilation of feudal law in Western Europe. Legal codification was part of the count's efforts to forward and somehow control the process of feudalization which started during the reign of his weak father, Berenger Ramon. Another major contributor was the Church acting through the institution of the Peace of God. This established a general truce among warring factions and lords in a given region for a given time. The earliest extant date for introducing the Peace of God in Western Europe is 1027 in Catalonia, during the reign of Ramon Berenguer the Old.

He was succeeded by his twin sons Ramon Berenguer II and Berenguer Ramon II.

Ramon Berenguers's marriages and descendants

• First wife, Isabel (or Elisabeth) of Narbonne or of Béziers
  • Berenguer (died young)
  • Arnau (died young)
  • Pere Ramon (1050-1073?) -> murdered his father's wife, Almodis, and was exiled
• Second wife, Blanca (origin unknown)
• Third wife, Almodis de La Marche, countess of Limoges
  • Berenguer Ramon II, Count of Barcelona the Fratricide (1053/54-1097)
  • Ramon Berenguer II, Count of Barcelona the Towhead (1053/54-1082)
  • Inés -> married Hugh d'Albo
  • Sancha -> married Guilhem Ramon, count of Cerdagne