Boston Red Sox has won 9 World Series Ring. Ties with the Oakland Athletics to rank in the 3rd place being the franchise that won the most World Series Ring.
9 World Series ring were won in year 1903, 1912, 1915, 1916, 1918, 2004, 2007, 2013 and 2018.
1903 Boston Red Sox World Series Ring

In the series, Boston Red Sox came back from a 3-1 deficit, winning the final four games to capture the title.
Furthermore, such a large comeback would not happen again until the Pittsburgh Pirates came back to defeat the Washington Senators in the 1925 World Series, and has happened only 11 times in baseball history.
Lastly, Red Sox claimed their first World Series ring.
1912 Boston Red Sox World Series Ring

This series, featuring close games and controversial decisions, was regarded as one of the most exciting World Series of its era.
Nearly all of the games were close. Four games in this Series were decided by one run.
A fifth ended in a tie
A sixth was decided by two runs.
Game 7 was the only one with a margin greater than three runs. Two games, including the decisive Game 8, went to extra innings.
However, in Games 1 and 3, the losing team had the tying and winning runs on base when the game ended. To date, this is the only World Series to end on a sacrifice fly.
Lastly, winning their second World Series ring for the franchise.
1915 Boston Red Sox World Series Ring

In their only World Series before 1950, the Philadelphia Phillies won Game 1 before being swept the rest of the way.
In addition, it was 65 years before the Phillies won their next Series game.
Furthermore, the Red Sox pitching was so strong in the 1915 series that the young Babe Ruth was not used on the mound and only made a single pinch-hitting appearance.
Lastly, winning their 3rd World Series ring.
1916 Boston Red Sox World Series Ring

Casey Stengel shone on offense for the Robins in the 1916 Series, but the Red Sox pitching corps ultimately proved too much for the denizens of Flatbush.
The Sox’s Babe Ruth pitched 13 shutout innings in Game 2, starting a consecutive scoreless innings streak that would reach 29 in 1918.
As with the 1915 Series, the Red Sox played their home games at the larger Braves Field, and it paid off as they drew a then-record 43,620 people for the final game.
Brooklyn fielded some strong teams under their manager and namesake Wilbert Robinson in the late 1910s.
The Robins, also interchangeably called the Dodgers, would win the pennant again in 1920, but the American League teams were generally stronger during that interval.
Furthermore, it would be 39 years before the Dodgers would win their first World Series title in 1955.
1918 Boston Red Sox World Series Ring

Firstly, this is the fifth World Series ring won be the Boston Red Sox by dedeating the Chicago Cubs 4-2 on the world series game.
Secondly, 1918 championship would be the last Red Sox win until 2004. The drought of 86 years was often attributed to the Curse of the Bambino. The alleged curse came to be when Red Sox owner Harry Frazee traded the superbly talented but troublesome Babe Ruth (who was instrumental in their 1918 victory) to the New York Yankees for cash after the 1919 season.
Thirdly, the Chicago Cubs would not win their next World Series until 2016. The Cubs, who last won in 1908, won the National League but lost the Series in 1918, 1929, 1932, 1935, 1938, and 1945, allegedly stymied by the infamous Curse of the Billy Goat imposed during that latter Series.
Fourthly, the Red Sox, who had won the American League but lost the Series in 1946, 1967, 1975, and 1986, finally won the World Series in 2004 and then won again in 2007, 2013 and 2018. When the Red Sox won in 2018 (against the Los Angeles Dodgers), they became the first team to win the Fall Classic exactly one century apart.
After Game 6, it would be some 87 years until the Cubs and Red Sox would play again.
A three-game interleague match-up at Wrigley Field began June 10, 2005, and was Boston’s first visit to the park. The Cubs would not return to Fenway Park for nearly 94 years until a three-game interleague match-up beginning May 20, 2011.
2004 Boston Red Sox World Series Ring

The St. Louis Cardinals earned their berth into the playoffs by winning the NL Central division title, and had the best win–loss record in the NL.
However, the Boston Red Sox won the AL wild card to earn theirs. The Cardinals reached the World Series by defeating the Los Angeles Dodgers in the best-of-five NL Division Series and the Houston Astros in the best-of-seven NL Championship Series.
While the Red Sox defeated the Anaheim Angels in the AL Division Series. After trailing three games to none to the New York Yankees in the AL Championship Series, the Red Sox came back to win the series, advancing to their first World Series since 1986.
Furthermore, the Cardinals made their first appearance in the World Series since 1987. With the New England Patriots winning Super Bowl XXXVIII, the World Series victory made Boston the first city to have Super Bowl and World Series championship teams in the same year (2004) since Pittsburgh in 1979.
Boston Red Sox became the third straight wild card team to win the World Series; the Anaheim Angels won in 2002 and the Florida Marlins won in 2003.
Firstly, the Red Sox had home-field advantage in the World Series by nature of the AL winning the 2004 All-Star Game.
Secondly, in game one, Mark Bellhorn helped the Red Sox win with a home run, while starter Curt Schilling led the team to a game two victory by pitching six innings and allowing just one run.
Secondly, the Boston Red Sox won the first two games despite committing four errors in each. The Red Sox won game three, aided by seven shutout innings by Pedro Martínez. A home run by Johnny Damon in the first inning helped to win game four for the Red Sox to secure the series.
Lastly, the Cardinals did not lead in any of the games in the series.
Above all, Manny Ramírez was named the series’ Most Valuable Player. The Red Sox and Cardinals faced each other again in the 2013 World Series, which the Red Sox also won, this time 4 games to 2.
Winning the 6th World Series ring for the franchise after the championship draught for more than a decade.
2007 Boston Red Sox World Series Ring

Firstly, Terry Francona became the second Red Sox manager to win two World Series titles, following Bill Carrigan, who won the 1915 and 1916 World Series.
Including the last three games of the AL Championship Series, the Red Sox outscored their opposition 59–15 over their final seven games.
Secondly, Francona also became the first manager to win his first 8 World Series games.
The Rockies, meanwhile, became the first NL team to get swept in a World Series after sweeping the League Championship Series, and just the second team ever to suffer such a fate, following the Oakland Athletics in 1990.
Lastly, this fate would again be suffered by the 2012 Detroit Tigers, being swept by the San Francisco Giants in the World Series after sweeping the New York Yankees in the ALCS.
This was the 7th World Series ring won by the franchise.
2013 Boston Red Sox World Series Ring

Firstly, this was the fourth meeting of the Cardinals and the Red Sox in the World Series (previously meeting in 1946, 1967, and 2004).
Secondly, it was also the first World Series since 1958 to feature two teams with identical regular season records.
Thirdly, Winning in six games, the Red Sox clinched their first World Series championship at their home field of Fenway Park since 1918, and the most recent edition where the championship was clinched by the home team (the Dodgers won the 2020 World Series as the designated home team, but at a neutral site).
Lastly, David Ortiz was awarded the World Series Most Valuable Player Award. He became the first non-Yankee to win three World Series titles with one team since Jim Palmer.
Claiming the eighth World Series ring for the Boston Red Sox.
2018 Boston Red Sox World Series Ring

The 2018 World Series was the first since 2000 to feature two teams which had also reached the postseason in the prior year.
Additionally, the Red Sox became the first team to win two World Series exactly one century apart, as they had defeated the Chicago Cubs in 1918, while the Dodgers were the first team since the 2011 Texas Rangers, and the first NL team since the 1992 Atlanta Braves, to lose consecutive Fall Classics.
This was the 3rd straight World Series to be won by a team with 100+ wins, and the 5th straight to be won on the road.
Also, the 9th World Series ring and the last world series ring won by the franchise.