The 25-year-old, who spent the 2021/22 season on loan at Carrow Road from Manchester United, has been without a club since leaving promotion-winning Hull City in February.
Williams made just a single substitute appearance during his brief stint with the Tigers, with his last competitive start coming in December 2023 during a loan spell at Norwich's East Anglian rivals, Ipswich Town.
As he seeks to rebuild following a turbulent period on and off the pitch, the full-back will look to impress during the early stages of Rotherham’s pre-season programme and could feature in their opening friendly against non-league Parkgate on Friday evening.
His opportunity in South Yorkshire comes with the backing of the Millers’ new head of football, Steve McClaren, who shares a strong United connection after serving as Sir Alex Ferguson’s assistant before later taking charge of the England national team.
Brandon Williams made 29 appearances for Norwich in the 2021/22 campaign (Image: Daniel Hambury/Focus Images Ltd)
Rotherham’s new head coach Alex Bruce – son of Canaries Hall of Famer Steve – also has links to Old Trafford, having spent time in the club’s academy.
But unlike Bruce, who was released by United at the age of 16, Williams was once regarded as a hot prospect at the 20-time English top-flight champions, progressing through the youth ranks before making his senior debut as a 19-year-old in a Carabao Cup clash against Rochdale in September 2019.
He quickly established himself in the Red Devils’ first-team setup that season under boss Ole Gunnar Solskjaer, making 36 appearances.
After an impressive breakthrough campaign, the left-back made just 14 appearances the following term, prompting a loan switch to Norfolk in the summer of 2021.
Williams featured 29 times in all competitions as Norwich suffered relegation from the Premier League before later joining Ipswich in August 2023.
The left-back spent a season on loan at East Anglian Rivals Ipswich Town (Image: PA)
He made 17 Championship appearances for the Tractor Boys during their promotion campaign before departing from Manchester United upon the expiry of his contract that summer.
After spending a year away from football amid a suspended 14-month prison sentence, a three-year driving ban and 180 hours of community service relating to a high-speed crash, Williams returned to the game with Hull last summer.
The defender acknowledged his past mistakes and expressed a strong commitment to reviving his career.
"It was just a learning process. Things did happen, but like I said, I've learnt from them now,” he told Hull Live last August. "I'm growing up now; I'm not a young player anymore.
"It was difficult because everyone kind of forgot what I actually achieved; people don't understand that. I didn't even understand at the time what I've actually achieved (playing for Manchester United at such a young age). There are a lot of people in the world who would wish that for their child or something like that. It was upsetting that I've let a lot of people down; it's for me to get things right now. Like, I've always said as well, I don't want any sympathy from anyone.
"It was my actions; I took responsibility for them. I've apologised, and all I can do now is just focus on my football and get things right on the pitch, and I'm sure that people will appreciate that."