The 24-year-old former England youth international arrives at Ibrox after an eventful conclusion to last season, having spent the second half of the campaign on loan with Ipswich Town from Sunderland, making 16 Championship appearances as the Tractor Boys secured promotion to the Premier League.
Born in South Shields, Neil graduated from Sunderland's Academy of Light and made 201 senior appearances for the Black Cats, scoring 12 goals, before becoming a free agent this summer.
As captain, he led Sunderland to the Premier League via the 2024-25 play-offs, wearing the armband as Regis Le Bris' side celebrated a dramatic 2-1 victory over Sheffield United in the Wembley final.
Neil made 47 league appearances and scored twice during that campaign as Sunderland ended their eight-year absence from England's top flight.
Speaking to RangersTV, Neil said he was excited to begin a new chapter at Ibrox.
"It is a new chapter for myself, and I am really excited to be signing for Rangers," he said. "I'm really looking forward to what the next few years can bring.
"I have played for Sunderland for a number of years and the weight and expectation of the fans to win every week and the feeling of it making or breaking people's weekends is something that drives me.
"I've spoken to many people who have been here, and they said it's a very similar feeling, and as a character and a person that really drives me to give 110 per cent day in and day out, and I need that in my career."
Rangers manager Derek McInnes said he was delighted to bring the midfielder to the club.
"I'm absolutely delighted to welcome Dan to the club," McInnes said. "He will be an excellent addition to our squad.
"He is a technically gifted midfielder who is strong in possession, can contribute goals and brings tremendous energy to the team.
"At 24, we are signing a player who is hungry and ambitious, but who already possesses significant experience and leadership qualities, having captained Sunderland to promotion to the Premier League in 2025.
"I'm really looking forward to working with Dan throughout pre-season as we prepare for the challenges ahead."