The Oakland Athletics' 2006 season was their 39th in Oakland, California. It was also the 106th season in franchise history. The team finished first in the American League West with a record of 93–69.

The Athletics won their division (and reached the postseason) for the first time since 2003. The team was led, in large part, by eventual Hall-of-Famer Frank Thomas. Thomas, who was signed to a one-year contract in the offseason, hit a team-high 39 home runs over the course of the season. He ultimately finished fourth in American League MVP voting.

The Athletics managed to sweep the Minnesota Twins in the first round of the playoffs. In doing so, they advanced to the American League Championship Series for the first time since 1992. The sweep was Oakland's first playoff series victory since 1990. It stood as the only playoff series victory during the Billy Beane era until 2020. The Athletics would themselves be swept, 4 games to 0, by the Detroit Tigers in the ALCS.

The team saw a number of key departures at the end of the season. Free agent pitcher Barry Zito, the team's lone All-Star in 2006, signed with the rival San Francisco Giants following the team's ALCS loss. Additionally, Frank Thomas signed a two-year deal with the Toronto Blue Jays. The coaching staff experienced similar turnover, as manager Ken Macha and longtime third base coach Ron Washington departed. Macha was fired at seasons' end; Washington, by contrast, was hired to manage the division rival Texas Rangers. They would be replaced by Bob Geren and Rene Lachemann, respectively.

• November 29, 2005: Esteban Loaiza was signed as a free agent with the Oakland Athletics.^[1]
• December 9, 2005: Scott McClain was signed as a free agent with the Oakland Athletics.^[2]
• December 13, 2005: Milton Bradley was traded by the Los Angeles Dodgers with Antonio Perez to the Oakland Athletics for Andre Ethier.^[3]
• January 31, 2006: Frank Thomas signed as a free agent.^[4]