At the tender age of just 16 years and 38 days, Bellingham made his senior debut at Portsmouth.
In doing so he bettered a mark that had stood for 49 years.
Blues legend Trevor Francis made his Blues debut as a substitute against Cardiff City in September, 1970.
Francis was 16 and 139 days.
So Bellingham now stands proudly alone as the Club's youngest player.
And Bellingham became the third youngest starter in EFL competition history.
Bellingham was among 13 Academy products who featured in the 18.
He acquitted himself well in what became a difficult tie for Blues before being replaced in the 80th minute.
Geraldo Bajrami, Odin Bailey and Caolan Boyd-Munce, who came on for Bellingham, also got their Blues debuts.
England Under-16s captain, Bellingham has long been seen as the jewel in the crown of Blues Academy.
Born in Stourbridge, Bellingham joined Blues as an Under-8 in pre-Academy and has been in the youth system ever since.
He made his Under-18s debut aged 14 and broke into the Under-23s in March, coming on and scoring the winner at Nottingham Forest at the City Ground.
Bellingham made 12 appearances for the Under-23s last season - six starts, six as substitute - and scored on three occasions.
Blues have handled his development carefully and with sensitivity and despite the inevitable interest from some of Europe's biggest clubs, Bellingham became a Scholar in the summer.
A gifted, intelligent footballer, Bellingham can play in a variety of positions, most notably as a 10 or eight. Elegant and easy on the eye but also dynamic and an elusive dribbler, Bellingham can conjure goals for himself or provide for others with his vision.
He enjoyed a taste of life with the first team last season by being part of the squad at home and away games, joining in the warm-ups, and he has trained with the seniors on numerous occasions.
After Pep Clotet was appointed Head Coach, he was assimilated into the first team full-time when Blues reported back and went on the pre-season tour to Portugal.
Blues have been renowned for blooding young talent, and Bellingham joins an elite list of prodigies.
Here are Blues youngest players:
Jude Bellingham, August 2019 - 16 years, 38 days
Trevor Francis, September 1970 - 16 years, 139 days
Nathan Redmond, August 2010 - 16 years, 173 days
Jordon Mutch, August 2008 - 16 years, 268 days
Paul Tait, May 1988 - 16 years, 279 days
Steve Phillips, August 1971 - 17 years, 17 days.
Trevor Dark, February 1978 - 17 years, 19 days.