White, 28, was forced off in the first half at the London Stadium following a collision with West Ham winger Crysencio Summerville. He left the ground in a knee brace. Arsenal's official statement confirmed the diagnosis.
"Further to Sunday's match at West Ham United, subsequent assessments and specialist reviews have confirmed that Ben White has sustained a significant medial knee ligament injury, which will rule him out for the remainder of this season. Our medical team are now managing Ben's recovery and rehabilitation programme, with everyone fully focused on supporting the aim of Ben being ready for the start of our pre-season preparations."
The statement's explicit focus on pre-season rather than the Champions League final confirms he will not be available for the showpiece in Munich.
The Sun additionally reported the injury puts his place in England's World Cup squad under serious threat. Thomas Tuchel named his 55-man preliminary squad this week — whether White makes the final 26 will depend on how quickly he recovers across the coming weeks.
The timing is a significant blow for Mikel Arteta. First-choice right-back Jurrien Timber is also sidelined, leaving the Spaniard without his first or second choice option on the right side of defence for the most important match in the club's recent history.
Valencia loanee Cristhian Mosquera — primarily a centre-back — is expected to fill the right-back role in Munich. Arteta has also used Myles Lewis-Skelly and Kieran Tierney in emergency roles during the season.
Arsenal need only to avoid defeat in two of their final three Premier League matches to confirm the title ahead of Manchester City. Burnley at home, a trip to Bournemouth and a final day fixture against Brentford remain. The Champions League final is the last match of the season.