The 1965 NFL season was the 46th regular season of the National Football League. The Green Bay Packers won the NFL title after defeating the Cleveland Browns in the NFL Championship Game, the last before the Super Bowl era.

The NFL's war with the rival American Football League began to increase as the two leagues competed for the top players coming out of college. Prior to the season, both the NFL's Chicago Bears and the AFL's Kansas City Chiefs selected running back Gale Sayers in their respective league drafts. Sayers eventually decided to sign with the NFL's Bears in a victory for the established league. On the other hand, quarterback Joe Namath was selected by both the NFL's St. Louis Cardinals and the AFL's New York Jets, but Namath decided to play for the Jets after signing a $427,000 contract for three years.

This war between the AFL and the NFL would escalate until just before the 1966 season, when they would agree to merge and create a new AFL-NFL World Championship Game between the winners of the two leagues, that later would be known as the Super Bowl.

The 1965 NFL draft was held on November 28, 1964, at New York City's Summit Hotel. With the first pick, the New York Giants selected back Tucker Frederickson from Auburn University.

Each team played each of the six other teams in its division twice. In addition, each team played two of the seven teams from the other division to complete the 14-game schedule. Thus, each week's schedule included 6 intra-divisional games (3 from each division) and one inter-divisional game. In 1965 the Western Division dominated the Eastern Division winning 13 out of the 14 interdivisional games. The lone win for the Eastern Division was a 39–31 victory by Dallas over San Francisco in week eight.

As in 1964, the Eastern Division race started out as a battle between the Cardinals and the Browns. By Week Five (October 17), both had 4–1–0 records, but the Cards won only one more game after that, finishing 5–9. The Browns won all seven of their remaining divisional games during the same stretch, losing only their two inter-divisional games against Western opponents. The Browns had clinched the conference title by November 28.

In the Western Division race, Green Bay won its first six games before a 31–10 loss at Chicago on Halloween put it in a tie with the Baltimore Colts. In Week Eight (November 7), the Packers lost again, 12–7 to Detroit, while the Colts beat Chicago 26–21. Both teams won their next two games, but in Week Eleven, the Packers lost 21–10 to the Rams, and the Colts averted a loss by tying the Lions, 24–24. In Week Twelve, Green Bay closed the gap with a 24–19 win over the Vikings, while the Colts fell to Chicago, losing the game (13–0) and their star quarterback, Johnny Unitas, to a knee injury.

With backup Gary Cuozzo passing for the Colts, they met the Packers again, in Baltimore, on December 12, and Paul Hornung scored five touchdowns as Green Bay won, 42–27, to take a half-game division lead, 10–3 to 9–3–1. Along with the division lead, the Colts lost another quarterback when Cuozzo was injured. In the final weekend, the Colts were in Los Angeles for a Saturday game that they had to win but were losing 17–10. A tying touchdown by fourth-string quarterback Ed Brown helped the Colts knot the game 17–17, but a tie wasn't enough. It took Lou Michaels' field goal to get a 20–17 win and a 10–3–1 record. A Green Bay win the next day in San Francisco would have ended the race, and the Packers leading and were slightly more than a minute away from the title game, but the 49ers tied the game, 24–24, with 1:07 to play. Both Green Bay and Baltimore had 10–3–1 records, forcing a playoff for the day after Christmas.