Date of birth
Republic of Ireland
Aiden made his full League team debut for Millwall at Derby during the 2014/15 season - and has established himself as a regular member of the first team squad.
Aiden established himself at U21 level for the Republic and went on to appear for Millwall's first team against Southampton in the Capital One Cup in August 2014. His full debut followed on October 4th 2014 and his first goal for The Lions was a textbook header in a 2-2 draw at Brentford in March 2015.
He continued his excellent progress during the 2015/16 campaign, scoring 13 goals in 37 starts for Neil Harris' senior side, adding another 15 goals in 57 games in 2016/17.
Aiden's good form at the start of 2017/18 earned him a call-up to the Republic of Ireland squad for their World Cup Qualifiers against Moldova and Wales, and went on to feature 30 times, scoring four goals including a brace against Barnsley in the Emirates FA Cup Third Round.
He then went on to finally make his senior Irish debut in September 2018, and scored the opening goal against Poland which scooped the nation's Goal of the Year award.
In 47 games in 2018/19, O'Brien scored five times, most memorably in the Emirates FA Cup Quarter-Final against Brighton & Hove Albion at The Den.