The Pittsburgh Pirates are an American professional baseball team based in Pittsburgh. The Pirates compete in Major League Baseball (MLB) as a member club of the National League (NL) Central division. Founded as part of the American Association in 1881 under the name Pittsburgh Allegheny, the club joined the National League in 1887 and was a member of the National League East from 1969 through 1993. The Pirates have won five World Series championships, nine National League pennants, nine National League East division titles and made three appearances in the Wild Card Game.

Despite struggling in the 1880s and 1890s, the Pirates were among the best teams in baseball shortly after the turn of the 20th century. They won three consecutive NL titles from 1901 to 1903, played in the inaugural World Series in 1903 and won their first World Series in 1909 behind Honus Wagner. The Pirates took part in arguably the most famous World Series ending, winning the 1960 World Series against the New York Yankees on a walk-off home run by Bill Mazeroski, the only time that Game 7 of the World Series has ever ended with a home run. They also won the 1971 World Series, led by the talent of Roberto Clemente, and the 1979 World Series under the slogan "We Are Family", led by "Pops" Willie Stargell. After a run of regular-season success in the early 1990s, the Pirates struggled mightily over the following decades with 20 consecutive losing seasons from 1993 to 2012the longest such streak in American professional sports history. The Pirates returned to the postseason in 2013 and advanced to the NLDS. The team qualified for the postseason again in 2014 and 2015. The Pirates currently have the sixth-longest World Series championship drought (behind the Cleveland Guardians, Texas Rangers, Milwaukee Brewers, San Diego Padres, and Seattle Marinersall except the Guardians have never won a World Series), second-longest World Series appearance drought in Major League Baseball (behind only the Mariners, who have never appeared in a World Series), the longest pennant drought in the National League (their most recent showing being their victory in the 1979 World Series) the longest League Championship Series appearance drought in either league and are tied for the longest MLB division championship drought with the Colorado Rockies and Miami Marlins (the latter two teams having joined the NL as expansion teams the season immediately following the Pirates' most recent division title). From 1882 to 2021, the Pirates have an overall record of 10,62510,547 (.502 winning 'percentage').The Pirates are also often referred to as the "Bucs" or the "Buccos" (derived from buccaneer, a synonym for pirate). Since 2001 the team has played its home games at PNC Park, a 39,000-seat stadium along the Allegheny River in Pittsburgh's North Side. The Pirates previously played at Forbes Field from 1909 to 1970 and at Three Rivers Stadium from 1970 to 2000. Since 1948 the Pirates' colors have been black, gold and white, matching the other major professional sports teams in Pittsburgh, the Steelers and the Penguins (and the minor league Pittsburgh Riverhounds SC). These colors are derived from the flag of Pittsburgh, and Pittsburgh is the only North American city where all the professional sports teams share the same colors.

The Boston Red Sox are an American professional baseball team based in Boston. The Red Sox compete in Major League Baseball (MLB) as a member club of the American League (AL) East division. Founded in 1901 as one of the American League's eight charter franchises, the Red Sox' home ballpark has been Fenway Park since 1912. The "Red Sox" name was chosen by the team owner, John I. Taylor, circa 1908, following the lead of previous teams that had been known as the "Boston Red Stockings", including the forerunner of the Atlanta Braves. The team has won nine World Series championships, tied for the third-most of any MLB team, and they have played in 13. Their most recent World Series appearance and win was in 2018. In addition, they won the 1904 American League pennant, but were not able to defend their 1903 World Series championship when the New York Giants refused to participate in the 1904 World Series.

The Red Sox were a dominant team in the new league, defeating the Pittsburgh Pirates in the first World Series in 1903 and winning four more championships by 1918. However, they then went into one of the longest championship droughts in baseball history, dubbed the "Curse of the Bambino" after its alleged inception due to the Red Sox' sale of Babe Ruth to the rival New York Yankees two years after their world championship in 1918, an 86-year wait before the team's sixth World Championship in 2004. The team's history during that period was punctuated with some of the most memorable moments in World Series history, including Enos Slaughter's "mad dash" in 1946, the "Impossible Dream" of 1967, Carlton Fisk's home run in 1975, and Bill Buckner's error in 1986. Following their victory in the 2018 World Series, they became the first team to win four World Series trophies in the 21st century, with championships in 2004, 2007, 2013 and 2018. The team's history has also been marked by the team's intense rivalry with the New York Yankees, arguably the fiercest and most historic in North American professional sports.The Boston Red Sox are owned by Fenway Sports Group, which also owns Liverpool F.C. of the Premier League in England. They are consistently one of the top MLB teams in average road attendance, while the small capacity of Fenway Park prevents them from leading in overall attendance. From May 15, 2003, to April 10, 2013, the Red Sox sold out every home game—a total of 820 games (794 regular season) for a major professional sports record. Both Neil Diamond's "Sweet Caroline" and The Standells' "Dirty Water" have become anthems for the Red Sox.As of the end of the 2021 season, the franchise's all-time regular-season record is 9,718–9,014 (.519).