Connolly began his career as a scholar in the Derby County Academy, and had his first experience of first team football came when he was named as a substitute for Derby County's FA Cup 5th Round tie at home to Birmingham City in February 2010 before making his full debut as a late substitute in Derby's 2–0 victory over Cardiff City on the final day of the 2009–10 season. Although primarily involved with the youth team – scoring twice in a 6–1 win over Peterborough United in the FA Youth Cup -Connolly also appeared for the Derby County Reserves side which won the 2009–10 Central League Central Section title, starting three of his nine appearances and scoring the winner in a 1–0 win over Sheffield Wednesday. He was named as Derby's Scholar of the Year for the 2009/10 season and signed his first professional deal with the club on 8 July 2010. Connolly's career suffered a setback when he suffered a cruciate ligament injury during an Under 18's friendly in August 2010, which ruled him out for six months. Despite this setback he was given a new one-year contract extension, alongside compariate Jeff Hendrick, in January 2011 to take him through until Summer 2012. He returned to competitive action on 3 May 2011 when he appeared as a second-half substitute in Derby County reserves 4–0 victory at Sheffield United, which clinched the club's second consecutive totesport Central League title.
On 31 August 2011, Connolly joined Scottish First Division side Ayr United on loan until 31 December 2011. Connolly spent the majority of his time at Ayr on the substitutes bench as he featured 12 times for The Honest Men. Connolly was named on the Derby County substitute bench in a 2–0 defeat at Brighton & Hove Albion on 20 March 2012, being allocated squad number 34.
Connolly spent the 2017 season with Shamrock Rovers making four appearances in the 2017–18 UEFA Europa League.
Galway United
Connolly re-signed with Galway United in December 2017 ahead of the 2018 League of Ireland First Division season. He made his League debut for The Tribesmen in their 4–1 win over Athlone Town on Friday, 23 February.
Finn Harps
In December 2019, Connolly was announced as having joined Finn Harps F.C. for the 2020 League of Ireland Premier Division season. Ryan's personal sponsor for the season is .
International career
He has represented the Republic of Ireland at Under 15, 16 and Under 17 level. He was called up to the Republic of Ireland Under 19 for the first time, alongside fellow Derby County player Jeff Hendrick, on 29 July 2010.
