Born in Colchester, Dunne is the son of former Colchester United player, manager and Hall of Fame member Joe Dunne. Louis was born just 36 hours after Joe had played for the Colchester first team in Division Two, and his manager at the time Steve Wignall wanted his side to go out against Reading following his birth to "win for Louis". Dunne started his career with Colchester's Academy at the age of eight and joined the club's Elite Football Programme in 2011 at Thurstable School in Tiptree. He was offered a youth scholarship by the club in September 2012, and during the 2012–13 season he was playing above his age group with the under-15 and under-16 Colchester United sides. He again stepped up during the 2013–14 season, regularly playing for the under-18 side. Ahead of the 2015–16 season, Dunne was given the shirt number 41, and manager Tony Humes named him in his matchday squad to face Oldham Athletic in League One on 18 August, but he was an unused substitute. Dunne signed a three-year Professional Development contract with the club in January 2016. New manager Kevin Keen named Dunne in his matchday squad for Colchester's home game against Wigan Athletic on 12 March 2016. He was introduced as a 77th-minute substitute in place of West Ham United loanee Elliot Lee during the 3–3 with the second-placed side. Keen then named Dunne in his starting eleven for Colchester's home tie with Burton Albion at the Colchester Community Stadium on 23 April. He started the match, but was taken off at half-time for George Moncur when the U's were 1–0 down. The game finished 3–0 and relegated Colchester to League Two. During the 2016–17 season, Dunne failed to make a league appearance under John McGreal, but did make a single appearance in each of the three cup competitions Colchester were competing in. National LeagueSouth side Concord Rangers signed Dunne on an initial month-long youth loan on 25 August 2017. He made his debut on 26 August in Concord's 2–1 defeat by St Albans City. He made five league appearances. He suffered an anterior cruciate ligament injury during training in early 2018 which would rule him out of action for around nine months. Dunne signed a two-year contract extension with Colchester in May 2018. On 25 January 2020, Dunne joined Southern League Premier Division South side Farnborough on loan until the end of February. He made his debut the same day in a 2–0 home win against Beaconsfield Town. On 2 March, his loan was extended until the end of the season.
International career
Dunne is eligible to represent the Republic of Ireland through his father Joe. During the 2012–13 season, Dunne was called up by the under-15 side for a training camp. He then made his under-15 debut on 18 April 2013, starting in the 3–0 defeat to Finland. Dunne progressed to the under-17 team for the 2014–15 season, making his debut against Malta in August 2014, and then playing against Serbia the same year. Following his professional debut for Colchester United, Dunne was called up to the under-18 squad for their friendly match against England on 27 March 2016 at St George's Park. He started in the match, playing the first 45-minutes of what ended as a 4–1 defeat for Ireland.
