Pittsburgh Steelers owner Art Rooney II confirmed Mike Tomlin's decision to resign in a team statement on Tuesday.
"During our meeting today, Coach Tomlin informed me that he has decided to step down as our Head Coach," the statement read.
"Obviously, I am extremely grateful to Mike for all the hard work, dedication and success we have shared over the last 19 years. It is hard to put into words the level of respect and appreciation I have for Coach Tomlin."
Mike Tomlin's resignation comes a day after the Steelers were eliminated from the NFL playoffs by the Houston Texans, who won the Wild Card game 30-6 at Acrisure Stadium.
The Pittsburgh Steelers finished the regular season with a 9-8 record, extending Tomlin's record streak of 19 consecutive seasons of finishing above .500, and won the AFC North title after beating the Baltimore Ravens in the last game of the season.
The 53-year-old Tomlin, who hadn't won a playoff game since 2016, won one Super Bowl with the Steelers, beating the Arizona Cardinals 27-23 in Super Bowl XLIII.
By having Tomlin resign rather than be fired, the Pittsburgh Steelers retain the rights to the head coach, who is under contract through the 2027 season. It is expected that Tomlin will take up a role in television before becoming a prime trade candidate in 2027.
Three head coaches in 57 years
Mike Tomlin leaves the Steelers after a 19-year reign that saw the franchise go 193-114-2 in the regular season. Of the 20 playoff games Tomlin coached, the Steelers lost 12.
The Steelers reached the Super Bowl twice under Tomlin, who won his first and only title in the 2008 season. Two years later, in Super Bowl XLV, the Aaron Rodgers-led Green Bay Packers beat the Steelers 31-25. The Steelers only reached the AFC Championship Game once after their last Super Bowl loss.
Tomlin's resignation means the Pittsburgh Steelers will begin their first head coach search since 2007 and their fourth since 1969, when Hall of Famer Chuck Noll took over from Bill Austin. Noll was at the helm in Pittsburgh until his retirement in 1991, when Bill Cowher took over.
Under Noll, Cowher and Tomlin, the Steelers became a storied franchise by winning six Super Bowls, tied for the most among NFL franchises.
'My love for Pittsburgh will never change'
In another statement released by the Steelers, Mike Tomlin thanked the team ownership and players who supported him during his 19 years in Steel City.
"After much thought and reflection, I have decided to step down as head coach of the Pittsburgh Steelers," Tomlin started his statement.
"The organization has been a huge part of my life for many years, and it has been an absolute honor to lead this team. I am deeply grateful to Art Rooney II and the late Ambassador Rooney for their trust and support.
"I am also thankful to the players who gave everything they had every day, and to the coaches and staff whose commitment and dedication made this journey so meaningful."
Tomlin closed his statement out by thanking the Pittsburgh Steelers fans, while also looking at what might be ahead.
"I want to also thank Steelers Nation. Your passion, loyalty, and high expectations represent what makes this franchise truly special. Coaching in Pittsburgh is unlike anywhere else, and I will always take great pride in having been a steward of this team.
"While this chapter comes to a close, my respect and love for the Pittsburgh Steelers will never change. I am excited for what the future holds for this organization, and I will forever be grateful for my time coaching in Pittsburgh."