A four-seam fastball, also called a rising fastball, a four-seamer, or a cross-seam fastball, is a pitch in baseball. It is a member of the fastball family of pitches and is usually the fastest ball thrown by a pitcher. It is called what it is because with every rotation of the ball as it is thrown, four seams come into view. A few pitchers at the major league level can sometimes reach a pitch speed of over 100 mph. It is often compared with the two-seam fastball.

In baseball, the pitch is the act of throwing the baseball toward home plate to start a play. The term comes from the Knickerbocker Rules. Originally, the ball had to be thrown underhand, much like "pitching in horseshoes". Overhand pitching was not allowed in baseball until 1884.