The 21-year-old was loaned out to the Austrian side for the second half of the 2023-24 campaign, having excelled at Motherwell with six goals and five assists in 14 Premiership matches in the first half of the campaign.
Biereth continued to go from strength to strength with Sturm Graz, contributing nine goals and four assists from 22 games as Die Schwoazn unexpectedly dethroned Red Bull Salzburg as Austrian Bundesliga champions.
Biereth ended the campaign with a league and cup double to his name and also shone in continental action in the Europa Conference League, coming up with three goals in four knockout matches.
Despite his continued rise to prominence, Biereth seemingly does not have a long-term future at Arsenal, whom he is only under contract with for another year and is yet to make his senior debut for.
Biereth to become Sturm Graz's record signing
According to the Evening Standard, Biereth is now set to leave Arsenal permanently for Sturm Graz in a deal worth £4m, which will make him the Austrian side's most expensive player of all time.
The 21-year-old is now set to finalise his personal terms and complete his medical in the coming hours, after which he will become the latest academy product to leave the Gunners this summer.
Biereth departs Arsenal three years after the Gunners poached him from Fulham, whom he had scored 21 goals and set up 13 more in 21 Under-18 Premier League appearances for in 2020-21.
The Denmark Under-21 international quickly found his feet in Arsenal's academy ranks with 11 goals in 21 matches in the 2021-22 Premier League 2 season, while he also made the bench for Arsenal in the Premier League, FA Cup and EFL Cup.
Biereth was supposedly hopeful of forcing his way into Mikel Arteta's side, but all parties now recognise that a permanent exit is best for the striker's career, and he will have the chance to play in the Champions League with Sturm Graz next season.
Could Chido Obi follow Biereth out of Arsenal?
While Arsenal are yet to make any significant summer sales - only losing Mohamed Elneny, Cedric Soares and Arthur Okonkwo on free transfers - a handful of top academy prospects have decided that the Emirates is not the best place to further their careers.
Highly-rated attacker Amario Cozier-Duberry and promising defender Reuell Walters both rejected the chance to sign new deals, and there is continued uncertainty over the future of Chido Obi Martin.
The 16-year-old - who scored 32 goals for the Under-18s last season - is yet to agree terms over an Arsenal scholarship contract, even though the Gunners have reportedly made an improved offer to his camp.
However, Arsenal cannot tie Obi Martin down to a professional deal until he turns 17 on November 29, and both Bayern Munich and Borussia Dortmund are waiting to pounce.