The Baltimore Orioles are an American professional baseball team based in Baltimore. The Orioles compete in Major League Baseball (MLB) as a member club of the American League (AL) East division. As one of the American League's eight charter teams in 1901, the franchise spent its first year as a major league club in Milwaukee, Wisconsin, as the Milwaukee Brewers before moving to St. Louis, Missouri, to become the St. Louis Browns in 1902. After 52 years in St. Louis, the franchise was purchased in November 1953 by a syndicate of Baltimore business and civic interests led by attorney and civic activist Clarence Miles and Mayor Thomas D'Alesandro Jr. The team's current owner is American trial lawyer Peter Angelos.

The Orioles adopted their team name in honor of the official state bird of Maryland; it had been used previously by several baseball clubs in the city, including another AL charter member franchise also named the "Baltimore Orioles", which moved to New York in 1903 to eventually become the Yankees. Nicknames for the team include the "O's" and the "Birds".

The Orioles experienced their greatest success from 1966 to 1983, they played in six of their total seven world series during these years, winning three in 1966, 1970, and 1983. This era of the club featured several future Hall of Famers who would later be inducted representing the Orioles, such as third baseman Brooks Robinson, outfielder Frank Robinson, starting pitcher Jim Palmer, first baseman Eddie Murray, shortstop Cal Ripken Jr., and manager Earl Weaver. The Orioles have won a total of nine division championships (1969, 1970, 1971, 1973, 1974, 1979, 1983, 1997, 2014), seven pennants (1944 while in St. Louis, 1966, 1969, 1970, 1971, 1979, 1983), and three wild card berths (1996, 2012, 2016). The franchise was the last charter member of the American League to win a pennant, and the last charter member to win a World Series.

After 14 consecutive losing seasons between 1998 and 2011, the team qualified for the postseason three times under manager Buck Showalter and general manager Dan Duquette, including a division title and advancement to the American League Championship Series for the first time in 17 years in 2014. Four years later, the Orioles lost 115 games, the most in franchise history. The Orioles chose not to renew the expired contracts of Showalter and Duquette after the season, ending their respective tenures with Baltimore. The Orioles' current manager is Brandon Hyde, while Mike Elias serves as general manager and executive vice president.

The Orioles are also famous for their influential ballpark, Oriole Park at Camden Yards, which opened in 1992 in downtown Baltimore.

From 1901 through the end of 2021, the franchise's overall win–loss record is 8,845–9,873 (.473). Since moving to Baltimore in 1954, the Orioles have an overall win–loss record of 5,466–5,398 (.503) through the end of 2022.