Following the purchase of Aaron Ramsdale from Sheffield United last summer, Leno found his playing time with the Gunners severely restricted in the 2021-22 campaign.
The 30-year-old managed to rack up just eight appearances for Mikel Arteta's side across all competitions, four of which came in the Premier League.
With the impending arrival of Matt Turner from MLS side New England Revolution in the coming weeks, Leno has been deemed surplus to requirements according to The Sun.
The report suggests that Benfica possess a strong interest in bringing the German to the Primeira Liga ahead of the 2022-23 season, but that the current £8.5m price tag is proving to be a stumbling block as things stand.
Leno could be one of several fringe players leaving the Emirates Stadium in the coming weeks, as Arteta looks to boost his transfer budget after missing out on Champions League football.
Having made the move to Arsenal for around £22.5m from Bayer Leverkusen in 2018, Leno has gone on to make 125 appearances for the North London side during his four-year stay so far.
Monaco 
Stade Brestois 29 
Bordeaux 
Nimes 
Bayern Munich 
FC Augsburg 
Paris Saint Germain 
Toulouse 
CSKA Moscow 
FC Rostov 
Leicester 
Chelsea 
Valencia 
Betis 
Dynamo Kyiv 
Chornomorets Odesa 
Verona 
Inter 
Bayer Leverkusen 
FC Heidenheim 
Borussia Dortmund 
SC Freiburg 
VFL Wolfsburg 
Union Berlin 
Arsenal 
Nottingham Forest 
Everton 
Brentford 
Spartak Moscow 
Lokomotiv Moscow 
Rangers 
Dundee Utd 
Atletico Madrid 
Alaves 
Lens 
Marseille 
Ingulets Petrove 
Shakhtar Donetsk 
AC Milan 
Juventus 
ST Malo 
Manchester City 
Tottenham 
Eintracht Frankfurt 
Werder Bremen 
Girona 
Espanyol 
Feyenoord 
Heerenveen 
ST Etienne 
Montpellier 
Grenoble Foot 38 
Heart Of Midlothian 
Celtic 
Reims 
Lyon 
PSV 
Groningen