Yankees - Dodgers World Series 4 of 5 years: 1952-1956.

The National Basketball Association (NBA) finals starts tonight and the same two teams are playing for the championship for the fourth consecutive year.

https://www.basketball-reference.com/playoffs/

Year	Lg	Champion	Runner-Up

2018	NBA

2017	NBA	Golden State Warriors	Cleveland Cavaliers

2016	NBA	Cleveland Cavaliers	Golden State Warriors

2015	NBA	Golden State Warriors	Cleveland Cavaliers

This has been described as not just unusual but unprecedented in any of the top three North American professional leagues: NBA, NFL, MLB. However:

MLB comes pretty close with 4 of 5 years and another three consecutive years.

NBA also has 4 of 5 years: Celtics - Lakers.

NFL three consecutive years and several back to back.

https://www.baseball-reference.com/postseason/

1956 World Series	4-3	New York Yankees (97-57, AL) vs. Brooklyn Dodgers (93-61, NL)
1955 World Series	4-3	Brooklyn Dodgers (98-55, NL) vs. New York Yankees (96-58, AL)
1954 World Series	4-0	New York Giants (97-57, NL) vs. Cleveland Indians (111-43, AL)
1953 World Series	4-2	New York Yankees (99-52, AL) vs. Brooklyn Dodgers (105-49, NL)
1952 World Series	4-3	New York Yankees (95-59, AL) vs. Brooklyn Dodgers (96-57, NL)

The New York Giants played the New York Yankees in the World Series three consecutive years, winning the first two: 1921, 1922, 1923. The teams played in the same ballpark (Polo Grounds) in 1921 and 1922 before the Yankees moved into Yankee Stadium in 1923.

The Boston Celtics won the NBA title each year 1959-1966, beating the Los Angeles Lakers in four of five years: 1962, 1963, 1965, 1966. In the middle year the Celtics beat the San Francisco Warriors.

The New York Knicks played the Los Angeles Lakers in the NBA finals in three of four years 1970-1973: Knicks beat Lakers in 1970 and 1973; Lakers beat the Knicks in 1972. Gratuitous mention of the only two Knicks championships.

In the National Football League (NFL) the same teams played for the championship in two consecutive years only once during the Super Bowl era (1966 - 2017 seasons): Dallas Cowboys beat the Buffalo Bills 1993 and 1994. The Bills had already lost the two previous championship games to the Giants and Redskins. The NFL started playing a championship game in 1933.

The same teams played for the NFL championship in three consecutive seasons only once: Lions - Browns 1952, 1953, 1954. Lions won the first two.

The Green Bay Packers beat the Giants in 1961 and 1962.

The Baltimore Colts beat the Giants in 1958 and 1959.

1951: Rams beat Browns
1950: Browns beat Rams

1948: Eagles beat Cardinals
1947: Cardinals beat Eagles

1943: Bears beat Redskins
1942: Redskins beat Bears

1939: Packers beat Giants
1938: Giants beat Packers

1934: Giants beat Bears
1933: Bears beat Giants