The 2005 Seattle Seahawks season saw them win a conference championship for the first time in the team's history. They were the NFC representative in Super Bowl XL, a game they lost to the Pittsburgh Steelers. The Seahawks compiled a 13–3 record in the regular season, easily winning the NFC West and earning the NFC top seed, thus clinching home field advantage in the NFC playoffs for the first time in franchise history. There, they beat the Washington Redskins and Carolina Panthers to win the George Halas Trophy, and advance to their first ever Super Bowl. Combining the regular season and postseason, the Seahawks finished with a perfect 10–0 record at Qwest Field. The 2005 team was widely considered the best team in club history until the Super Bowl XLVIII championship. The 2005 season was also the team's 30th anniversary season in the National Football League.
The Seahawks touted Pro Bowlers on offense, and boasted season MVP, running back Shaun Alexander, who would eventually break Priest Holmes's previous single-season rushing touchdown record, with 28 TDs. Alexander also led the league in rushing yards for the second consecutive year, which in turn helped the Seahawks lead the league in scoring. The offense was led by 7th-year veteran quarterback Matt Hasselbeck, who compiled a career-high and NFC leading 98.2 passer rating, while completing 65.5% of his passes, earning his second trip to the Pro Bowl. Walter Jones and Steve Hutchinson anchored the offensive line at left tackle and guard respectively, and Mack Strong effectively blocked and rushed from the backfield at fullback.
Although Seattle's strength was attributed to their offense, they were strong on the defensive side of the ball as well. The Seahawks compiled an NFL-leading 50 Quarterback sacks, with defensive end Bryce Fisher leading the franchise with nine, while defensive tackle Rocky Bernard added 8.5 and veteran defensive end Grant Wistrom recorded four. Despite starting two rookies at linebacker for most of the year, the Seattle linebacking corps played well, led by Pro Bowler Lofa Tatupu, who topped the team with 104 tackles and added four sacks, three interceptions, and one fumble recovery. In the secondary, Michael Boulware led the team with four interceptions and also tallied two sacks and one fumble recovery, however Seattle suffered injuries throughout the year, notably to free safety Ken Hamlin. A bright spot in relief, second-year cornerback Jordan Babineaux played well as he appeared in all sixteen games for Seattle, intercepting three passes and making 61 tackles. For the season, the Seahawks defense ranked 7th in points allowed, surrendering just 271 total, 181 fewer than the Seahawks offense scored.