The 45-year-old was forced to vacate the cockpit of his 23XI Racing Toyota last July, just two months after taking the 34th win of his career at Kansas, when he suffered a concussion at Pocono.
In October, he announced that he would not return as a full-time driver in 2023, allowing Tyler Reddick to make his switch from Richard Childress Racing one year earlier than planned.
There was still hope that Busch could be back in select starts, with 23XI Racing co-owner Denny Hamlin leaving the door open for Busch to drive for the team again. He has since remained close to the action, mentoring both Reddick and Bubba Wallace, while also serving as a brand ambassador for Monster Energy.
But Busch revealed on Saturday ahead of the final race of the regular season at Daytona that the 2017 Daytona 500 winner would not be adding to his 776 Cup starts, dating back to 2000.
In a video announcing his retirement, Busch explained that the decision had been made in consultation with his medical team.
"Sometimes father time can catch up to your dreams," he said.
"My incredible team of doctors and I have come to the conclusion that at this point in my recovery there are just too many obstacles for me to overcome and get back to 100%.
"So after 23 years behind the wheel and 45 years of living and breathing this dream, I am officially announcing my retirement from NASCAR Cup Series competition."
Busch earned earned 28 poles between 2000 and 2022 with five different race teams, and notably won both the Coke 600 and All-Star Race in 2010. He also led over 10,000 laps.
Earlier this year, he was named as one NASCAR's 75 Greatest Drivers, having become the first driver to win a Cup title to the playoff format introduced in 2004.
Busch has constantly updated the media regarding his recovery process and previously said that "everyday life is normal".
It was speculated that Busch planned to retire at the end of the 2023 season, but the accident forced those plans to change abruptly.
"Everything just happened a year sooner than I expected them to and I’m happy with where everything sits," said Busch in February.
He won at least one race in 19 of his last 21 seasons and ends his career 25th on the all-time wins list, currently tied with fellow Cup champion Martin Truex Jr.
