A uniform is a type of sportswear worn by baseball players, and sometimes by non-playing personnel such as managers and coaches. Modern uniforms have the names and uniform numbers of the players on them; color differences and insignia are mainly used to distinguish players from the two teams. Insignia often include shoulder patches depicting either the team crest or a geographic marker such as the state flag, and any commemorative patches highlighting a special event (e.g. hosting the All-Star Game), or paying tribute to a recently-deceased former player of team official.
The first uniforms, worn by the New York Knickerbockers Baseball Club, were composed of blue woolen trousers, white flannel shirts and straw hats. Since then, the uniform has changed dramatically, such as replacing straw hats with regular baseball caps and displaying the player's last name.
Uniforms are also worn by fans to indicate their allegiance. In these cases, it is rare that the full uniform is worn; this is usually limited to the cap and/or jersey of one's favorite team.
- Riles, Robert. American Chronicle. www.americanchronicle.com.
- The history of the baseball uniform at the National Baseball Hall of Fame. exhibits.baseballhalloffame.org.
- Anthony Castrovince: "Players poll: Who has MLB's best uniforms?", mlb.com, May 17, 2019. 
- Michael Clair: "The 15 weirdest baseball uniforms ever worn: Cover your eyes", mlb.com, June 27, 2020. 
- Michael Clair: "The 10 most iconic Negro Leagues uniforms: Uniforms as great as the players who wore them", mlb.com, August 14, 2020. 
- Michael Clair: "The 10 best shoulder patch logos in baseball: This is the epitome of wearable art", mlb.com, September 7, 2020. 
- Erin R. Corrales-Diaz: The Iconic Jersey: Baseball X Fashion, Giles Ltd., Lewes, UK, 2021. ISBN 978-1-911282-88-4
- Chris Landers: "Why exactly do managers wear uniforms in the dugout? No one would ever ask Belichick to wear shoulder pads", mlb.com, January 22, 2020. 
- Marc Okkonen: Baseball Uniforms of The 20th Century: The Official Major League Baseball Guide, Sterling Publishing Company, New York, NY, 1991. ISBN 978-0806984902
- Todd Radom: Winning Ugly: A Visual History of the Most Bizarre Baseball Uniforms Ever Worn, Sports Publishing LLC, New York, NY, 2018. ISBN 9781683582281
- Stephen Wong and Dave Grob: Game Worn: Baseball Treasures from the Game's Greatest Heroes and Moments, Smithsonian Books, Washington, DC, 2016. ISBN 978-1588345714