The Browns were founded in 1946 and were originally members of the AAFC, winning the league title in each of the four years of the AAFC's existence. They were integrated into the NFL along with two other former AAFC teams in 1950, and they continued to have success in the new league. The early years of Browns football were defined by the stellar play of quarterback Otto Graham (Graham, Otto) and the innovative coaching of Paul Brown (Brown, Paul), both members of the Hall of Fame, who guided the team to 10 divisional titles in as many years and 7 championships. These early Browns teams also featured Lou “The Toe” Groza, a kicker and offensive lineman, and Marion Motley (Motley, Marion), a bruising running back who was one of the first African Americans to play professional football. In 1957 Cleveland drafted running back Jim Brown (Brown, Jim), who would set every major NFL rushing record during his nine-year career and gain the status of possibly the greatest football player of all time. The team advanced to the NFL conference championship game twice in the five seasons after Brown retired, but they entered into their first prolonged period of mediocrity in the 1970s, from which they emerged briefly in the 1979–80 season due to the frequent last-minute heroics of a team dubbed the Kardiac Kids.

Quarterback and Ohio native Bernie Kosar was drafted in 1985 and led the Browns to five appearances in the play-offs in his first five years in the league. The Browns lost two memorable AFC championship games to John Elway (Elway, John) and the Denver Broncos during this span, each of which is remembered by Browns fans by an epithet describing the last-minute events responsible for Cleveland's downfall: “The Drive” (1987) and “The Fumble” (1988). The mid-1980s also saw the advent of the Dawg Pound, a section of the end-zone bleachers of the team's home stadium where a rowdy group of often-costumed fans sat, solidifying the image of Browns supporters as some of the most vocal and devoted fans in the NFL.

The 1990s brought much darker times for the Browns. Owner Art Modell—who had been losing money for years because of an unfavourable stadium lease with the city—orchestrated a move that sent the team to Baltimore in 1996, breaking the hearts of Cleveland's many loyal fans and shocking many football observers nationwide. The NFL arranged to keep the Browns' name, logo, colours, and history in Cleveland, and the league promised the city a new team in the near future. Cleveland was without a franchise until 1999, when local businessman Al Lerner purchased an expansion team that assumed the Browns' name and history. While the expansion Browns earned a play-off appearance in 2002, the team has yet to match the success of its previous incarnation.