The history of the Athletics Major League Baseball franchise spans the period from 1901 to the present day, having begun as a charter member franchise in the new American League in Philadelphia before moving to Kansas City in 1955 for 13 seasons and then to the San Francisco Bay in Oakland, California, in 1968. The team endured numerous attendance issues stemming from the aging Oakland Coliseum before the MLB owners approved the team's application to relocate to Las Vegas, Nevada in 2023. With four locations, the A's have had the most homes of any MLB team.

Major League Baseball (MLB) is a professional baseball league and the highest level of organized baseball in the United States and Canada. One of the big four major leagues, MLB comprises 30 teams, divided equally between the National League (NL) and the American League (AL), with 29 in the United States and 1 in Canada. Formed in 1876 and 1901, respectively, the NL and AL cemented their cooperation with the National Agreement in 1903, making MLB the oldest major professional sports league in the world. They remained legally separate entities until 2000, when they merged into a single organization led by the Commissioner of Baseball. MLB is headquartered in Midtown Manhattan.