Born in Stoke-on-Trent and raised in the Chesterton area of Newcastle-under-Lyme, Ramsdale joined Sheffield United in 2013. After graduating from Sheffield United's youth academy, Ramsdale signed a scholarship with the club in May 2014. Ramsdale appeared twice as an unused substitute during the 2015–16 season against Coventry City and Scunthorpe United. In May 2016, he signed his first professional contract with the club. Ramsdale made his professional début starting in a 6–0 home victory over Leyton Orient in the FA Cup, keeping a clean-sheet in the process. He also made another appearance in the FA Cup against Bolton Wanderers but lost 3–2.
AFC Bournemouth
On 31 January2017, he was signed by Premier League club AFC Bournemouth for an undisclosed fee believed to be in the region of £800,000. However, the move was reported to cost £1 million. Ramsdale was on the bench for the final game of the 2016–17 season against Leicester City.
Football League loans
In the January 2018transfer window, Ramsdale was loaned out to Chesterfield for the rest of the 2017–18 season. Ramsdale made his Chesterfield debut against Accrington Stanley on 6 January 2018, but scored an own goal after he "allowed a seemingly harmless Jackson strike from the right to squirm into the net", in a 4–0 loss. A week later, against Luton Town, he kept a clean sheet in a 2–0 win. Throughout the 2017–18 season, Ramsdale made 19 appearances in total for the club in League 2, but was ultimately unable to help prevent the club from suffering relegation to the Vanarama National League. On 4 January 2019, Ramsdale joined AFC Wimbledonon loan until the end of the 2018–19 season. The next day, Ramsdale made his debut for the Dons in a 3–2 FA Cup third round victory over Fleetwood Town at Highbury Stadium. His league debut came a week later in a 1–1 draw with Coventry City at the Ricoh Arena. Throughout the 2018–19 season, Ramsdale made 20 appearances in total for the club in League One, and in doing so he won the club's Young Player of the Season Award for his performances in goal, as Wimbledon achieved survival in League One despite being 10 points from safety in February.
Premier League breakthrough
Ramsdale made both his Premier League debut, and his full debut for Bournemouth, on the opening day of the 2019–20 season, in a 1–1 draw against former team Sheffield United. Ramsdale established himself as Bournemouth's first choice keeper throughout the first few months of the 2019–20 season, starting every single Premier League game for the club from the opening day of the season, right up until the 12th January game against Watford at home, which he missed due to injury. He returned to the side in the very next Premier League game, a 1–0 loss to Norwich City. He signed a new, long-term contract with the club in October 2019. That same month, Ramsdale's form for the club saw him win the club's Player of the Month award for October, keeping two clean sheets in the games against Norwich City and Watford. His form continued in the next few months, as he once again picked up the clubs Player of the Month award in January for another string of excellent performances, including a Man of the Match winning display against Brighton & Hove Albion.
International career
Ramsdale has represented England at Under 18, Under 19, Under 20 and Under 21 level. He was first called up by England U18 in March 2016, where he made his debut on his debut for the side, in a 4–1 win over Republic of Ireland U18 on 27 March 2016. He went on to make two appearances for the England U18 side. In August 2016, Ramsdale was called up by England U19, where he made his debut on 4 September 2016, in a 1–0 loss against Belgium U19. Ramsdale started all five games for the England under-19 side that won the 2017 UEFA European Under-19 Championship. During the tournament, Ramsdale kept three clean sheets in five matches. After winning the UEFA European U19-Championship, Ramsdale was called up by England U20 in August 2017, where he made his debut on 4 September 2017, in a 0–0 draw against Switerzland U20. On 18 May 2018, Ramsdale received a call up to England U21s for the first time by Manager Adrian Boothroyd, for the Toulon Tournament with Englands group containing fixtures against Qatar U21s, China U21s and Mexico U21s. Ramsdale made his first cap for the England u21 squad on 1 June 2018, playing the full 90 minutes in a 4–0 win against Qatar.