The Texans said the team and Watt "mutually agreed to part ways." Watt also released a video Friday on social media. He said he met with Texans ownership and requested his release.
Watt joined the Texans as the No. 11 overall pick in the 2011 NFL Draft. He is the franchise's all-time leader in sacks (101), forced fumbles (25) and fumble recoveries (16).
Watt, 31, signed a six-year, $100 million contract extension with the Texans in 2014. He was set to make $17.5 million in 2021.
"Change is never easy, especially when it involves the ones you love," Texans owner Cal McNair said in a news release.
"J.J.'s impact on not only our organization, but the entire Houston community, is unlike any player in our franchise's history. I told J.J. earlier this week that we will forever consider him a Texan."
Watt had 52 total tackles, seven passes defensed, five sacks, two forced fumbles, a fumble recovery and an interception for a touchdown in 16 starts last season. He started all 16 regular-season games in seven of his 10 seasons in Houston
The 6-foot-5, 288-pound pass rusher missed eight games in 2019 due to a torn pectoral injury. He missed 11 games in 2017 after he sustained a broken leg. Watt also played through several back injuries.
"I came here 10 years ago as a kid from Wisconsin who had never been to Texas before," Watt said in a video he posted to social media. "Now, I can't imagine my life without Texas in it.
"Since [draft] day, I have tried to do everything in my power to work and earn [fans'] respect and to try and make you proud on and off the field.
"You guys have given me everything and more and I can only hope that you feel like I have given you everything I have."
Watt was known as a philanthropic pillar in the Houston community. From 2017 through 2018, he raised more than $41 million in donations to assist those impacted by Hurricane Harvey. Watt went on to win the Walter Payton NFL Man of the Year award for those efforts.
He also started the Justin J. Watt Foundation to help underserved children. The foundation has provided more than $6 million in funding to schools and organizations that have insufficient funding for -- or lack -- after-school athletic programs.
"We take solace in knowing that this is not a goodbye but a 'see you soon,'" McNair said.
"For now, we will build upon the foundation that J.J. created here and forge ahead with our unwavering mission to bring a championship to our city, create memorable experiences for our fans and do great things for Houston."