He was a youth product of Ipswich Town but was not offered a professional contract and thus signed for Grimsby Town in 2006. He remained with Grimsby for a further four years in which he earnt international caps for England U18 as well as becoming the club captain at a young age. In his final full season he scooped the board in the club's player of the season ceremony. Grimsby Town cashed in on him in 2010 by selling him to Peterborough United after an initial loan deal. Whilst with Peterborough he represented England U21s.
Bennett was born in Grays, Essex. He came to prominence in 2006 when Grimsby Town's youth team manager at the time, Neil Woods swooped to sign him after he was let go by the youth setup at Ipswich Town. Initially joining the club as part of the youth team midway through the 2006–07 campaign, he was soon promoted to the first team, managed at the time by Alan Buckley. Bennett would make his professional debut as an 88th-minute substitute, replacing Danny Boshell in a 2–1 win over Milton Keynes Dons in April 2007. 21 days later he became the club's youngest ever captain, aged only 17 years old when Grimsby's all-time record appearance holder John McDermott passed him the skippers armband after being substituted in the local derby with Lincoln City.
In the summer of 2007 Bennett had re-established himself as one of the club's favoured centre backs, and in this he was handed the number 5 shirt for the coming season, which had previously been worn by such 'luminaries' as Tony Crane and Ben Futcher. He scored his first goal in professional football on the opening day of the 2007–08 season when his header from six yards opened the scoring in the 1–1 draw with Notts County at Blundell Park. In that same season, Bennett largely was favoured in the place of club captain Justin Whittle in the heart of Town's defence, and he went on to play in the club's Football League Trophy final defeat too Milton Keynes Dons at Wembley Stadium. In May 2008, Bennett was given the "Supporters Young Player of the year" for the 2007–2008 season.
With the appointment of Mike Newell as first team manager in October 2008, Bennett was handed the captain's arm-band for the remainder of the 2008–2009 campaign aged only 18. This was down to the fact that the new signing Matthew Heywood, who had also been designated the new club captain had fallen out of favour following several unconvincing performances, and Newell had preferred a youthful back pairing of Bennett and Rob Atkinson to the veteran duo of Heywood and Richard Hope. Bennett was ever present for the club during the 2008–09 season, and his consistently solid performances throughout a very difficult season for Grimsby saw Bennett win firstly the PFA Player of the Month for February, which would eventually be followed by several club accolades. He swept the board at the GTFC Player of the Year ceremony in May 2009, claiming the "Supporters Player of the Year" award, ~"Supporters Young Player of the year" as well as many other minor awards. Newell made repeated reference to Bennett's professionalism and maturity, and his unflappable playing style in particular was impressive for such a young defender, whilst his height made him an asset at set pieces. Also Bennett was described as comfortable on the ball.
On 13 May 2009, Grimsby were reported to have turned down a bid from Peterborough United after United's Director of Football Barry Fry publicly revealed that The Mariners had politely turned down a proposed move, mentioning that Grimsby said 'thanks for the interest but we wouldn't sell him for £1m'. On 13 June, United stepped up in their aim to sign Bennett, and offered Grimsby a largely superior offer to their previous one. Grimsby chairman John Fenty rejected the offer three days later mentioning that he did not feel it was in the club's best interest to let Bennett go. A week later Bennett confirmed he would be staying with Grimsby for the unforeseeable future by signing a new four-year deal to keep him at Blundell Park until the end of the 2012–13 season.
Bennett eventually did a u-turn and signed for Peterborough United on 23 October 2009 on an initial three-month loan deal with a view to a permanent move. Grimsby chairman John Fenty had a change of heart, and following a slow start to the season for his club, he decided to cash in on the Town skipper literally only days after sacking manager Mike Newell. Posh manager Darren Ferguson said of the transfer: "Ryan is an excellent signing for us, he has potential and fits in with our policy of bringing good, young players to the football club". Bennett made his loan at London Road permanent on 23 January 2010, signing a four-and-a-half-year contract, with Grimsby reportedly receiving £500,000, possibly rising to £1 million. Bennett scored against Barnsley on 3 December but Barnsley won 4–3. Bennett's final game for Peterborough was away at Doncaster, the Posh were 1–0 down in stoppage time until Bennett went down the wing and hooked the ball into the area for Tyrone Barnett who headed in on his debut after coming off the bench.
On 31 January 2012, Bennett signed for Premier League side Norwich City, for a reported £3.2 million. Club manager Paul Lambert said of the transfer: "I'm delighted we have signed Ryan. He's made a bright start to his career at Grimsby and Peterborough; he's an England U21 international and he's got so much potential." Peterborough United defender Gabriel Zakuani compared Ryan Bennett's move to Norwich to a "divorce". As part of the deal Bennett was immediately loaned back to Peterborough until the end of the month. Bennett was expected to sign for Swansea City and had begun the drive down to the Liberty Stadium only to be rung up and told to head for Norwich when the deal fell through. A 25% sell on clause meant that former club Grimsby Town earned £800,000 from the deal, with Grimsby chairman John Fenty revealing that Barry Fry had failed in an attempt to buy out the clause. Bennett's Norwich debut came on 31 March against Fulham, playing alongside Zak Whitbread and Elliott Ward in a 3–5–2 formation. He started every game for the rest of the season, earning rave reviews about his performances.
He scored his first goal for the club against Reading on 20 April 2013, which Norwich won 2–1. He was voted as Norwich's Man of the Match for his performance, and would proceed to also achieve that feat twice more in the following home matches against Aston Villa and West Brom, the latter of which his shot was deflected off Gareth McAuley after a Wes Hoolahan free-kick and into the net. Bennett scored his first goal of the 2013–14 season in a crucial home game against Hull City, where his 87th-minute header gave struggling Norwich a 1–0 victory. The goal eased pressure on manager Chris Hughton, who had recently been under-fire for a string of constant poor performances dating back to early 2013.
In May 2017, it was announced that Bennett would be released when his contract expires.
On 31 May 2017, he signed a three-year deal with Wolverhampton Wanderers.
Bennett was called up for the England national under-18 team that faced Austria at Victoria Park on 16 April 2008. It was his first England call-up. He played the full game in the 2–0 victory. On 29 September 2011, Bennett was called up to the under-21 team for the first time by Stuart Pearce. He made his debut in a 2–1 win away to Norway on 10 October 2011.As of match played 29 April 2017.
Grimsby TownSupporters Young Player Of The Year: 2008, 2009
Football League Awards Apprentice of the Year: 2008
PFA Player of the Month: February 2009
Supporters Player Of The Year: 2009
Peterborough UnitedFootball League One play-offs: 2010–11