The Gunners have announced PRIME, founded by KSI and Paul, as the club's new official drink, replacing Gatorade.
The two internet stars rose to fame as 'vloggers' on YouTube and became business partners after two fights in the boxing ring.
KSI is a childhood Arsenal fan and described the Gunners partnership as a dream come true.
Speaking to the Arsenal website, KSI said: "Honestly, I can't believe it, this is a childhood dream of mine.
"From watching Arsenal tear up the Premier League in the early 2000's to now being associated with Arsenal officially with PRIME, it's a dream come true and I'm still pinching myself!
"This is a huge moment and I'm so glad it's with the team I support."
The 29-year-old's relationship with Arsenal has not always been so joyous, though, judging by a tweet from 2019.
He said: "I'm actually sick of being an Arsenal fan. CBA with this club."
KSI, real name JJ Olatunji, beat Paul in their second bout after the first was ruled a draw - and will return to the ring against Alex Wassabi on August 27 at the O2 Arena in London.
Paul, meanwhile, fought boxing legend Floyd Mayweather in an exhibition bout last summer and could take on Dillon Danis in the near-future.
"To be able to sponsor Arsenal with Prime and have it at the stadium for everyone to drink including the players!" Paul said.
"Feeling good about Arsenal this season too so I'm excited.
"Prime is now the official sports drink of Arsenal. Madness."