List of Major League Baseball records considered unbreakable

The following Major League Baseball records are generally considered unlikely to ever be broken. The information is compiled from various sources including sportswriters, players, and fans. Many of these were initially set by either freak occurrences of greatness or during the early decades of baseball when certain rules, techniques, and fundamentals were in place that have since drastically evolved, making it almost impossible to replicate such feats in today's game.

Set by Cy Young, 1890–1911. Highlights include five 30-win seasons and fifteen 20-win seasons. The next closest player is Walter Johnson, with 94 fewer wins at 417; he was the only other player to have reached 400. The most wins by a pitcher who played his entire career in the post-1920 live-ball era is Warren Spahn's 363.

For a player to accomplish this, he would have to average 25 wins in 20 seasons just to get to 500. In the past 38 years, only 3 pitchers (Ron Guidry in 1978, Bob Welch in 1990, and Steve Stone in 1980) have had one season with 25 wins. Between 2000 and 2009, the Major League leader finished each year with an average of 21. The active leader in career wins entering the 2017 season is the 43-year-old Bartolo Colón with 233 wins.

Set by Old Hoss Radbourn, in 1884. Most pitchers in today's game start 30–35 games per season, and thus do not start enough games to break the record. The most games started by a pitcher in the 2014 season was 34, accomplished by six pitchers. This means that even if a pitcher were to win every game started in this scenario, he would still fall 25 wins short of tying Radbourn's record. Although relief pitchers often appear in more than the requisite number of games, they rarely record ten wins in a season. To put this record in further perspective, the last pitcher to win 30 games in a season was Denny McLain in 1968 and the last pitcher to win 25 games in a season was Bob Welch in 1990. Also, the most wins in a season by any pitcher in the 21st century is 24, by Randy Johnson in 2002 and Justin Verlander in 2011; no other pitcher in this era has had more than 23 in a season.

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