Baseball law refers to the various civil statutes, local ordinances, and court decisions pertaining to the game of baseball and its institutions, as distinguished from the Rules of Baseball, which are a private codification of rules governing the internal workings of baseball games.

Throughout the history of baseball, the rules have frequently changed as the game continues to evolve. A few common rules most professional leagues have in common is that four balls is a base on balls, three strikes is a strikeout, and three outs end a half-inning.