Kristoffer Vassbakk Ajer was born on 17 April 1998 in Rælingen, Norway. A product of IK Start's youth system, he joined Celtic as a teenager in 2016 and spent five formative years in Glasgow, developing into one of the most technically gifted central defenders in Scottish football. His composure on the ball, aerial ability and reading of the game drew admiring glances from several top European clubs.
In August 2021, Brentford paid around £13 million to bring Ajer to the Premier League, where he has established himself as a reliable and composed right-sided centre-back under Thomas Frank. Despite a period disrupted by a calf muscle injury that required surgery and cost him much of 2022-23, he returned to become a regular fixture in Brentford's back line as the club settled into Premier League life.
For the Norwegian national team he has been a consistent presence since making his senior debut, accumulating considerable caps and serving as a dependable defensive pillar as Norway pushed through their qualifying campaigns. His ability to play out from the back suits Norway's possession-oriented approach under their coaching staff.
Standing around 1.96 m, Ajer is an imposing yet technically refined central defender. His combination of physical stature and technical assurance on the ball makes him an asset in the modern high defensive line, and he is regarded as one of Norway's most complete defenders of his generation.